FERREN, Associate Judge:
Petitioner William D. Martin asks for review of an order of the Police and Firefighters Retirement and Relief Board (Board) denying his application for disability retirement from the Metropolitan Police Department. The Board concluded that Martin’s physical injuries to his wrist and hand did not disable him “for useful and efficient service in the grade or class of position last occupied.” D.C.Code § 4-607(2) (1981); see id. § 4-616(a). The Board’s ruling was not “in accordance with law,” id. § l-1510(a)(3)(A) (1987 Replacement), for the Board failed to make a specific finding that Martin’s assigned work is “useful and efficient” service to his department. Martin’s testimony raised this issue, and thus we remand for the Board to determine whether Martin has been disabled for service that is both useful and efficient, given the department’s needs and Martin’s capabilities.
I.
Martin joined the Metropolitan Police force in 1965. He had attained the rank of sergeant in February 1979 when he was shot in the wrist while attempting to execute a search warrant. During the four years following his injury, Martin underwent four operations to repair his damaged left wrist and to mitigate the pain he continued to experience. He sporadically performed some form of limited duty between April 1980 and his fourth operation in April 1983, when he went on extended sick leave. Since August 1985, Martin has performed a variety of light duty tasks with the police department.
Martin first applied for disability retirement in 1982. Although his wound had permanently disabled him from returning to full duty, the Board found Martin capable of performing a useful and efficient light duty alternative and, accordingly, denied his claim. Martin applied a second time for disability retirement in June 1984, but, because the Board found that Martin had presented no new evidence, the Board again denied his claim. When his doctors indicated that Martin’s condition had grown worse, he sought disability retirement a third time in October 1985. It is the denial of this claim that Martin now appeals. The decision and its evidentiary bases are set forth in the Board’s “Findings of Fact, Conclusions of Law, and Decision” (Decision) dated November 18, 1985.
At Martin’s October 1985 hearing, the Board received evidence from a variety of sources. Dr. Cornelius Frey had examined Martin more than forty times since his injury and had performed all four operations on Martin’s hand. Dr. Frey testified that, while Martin retained limited use of the fingers in his left hand, his thumb and index finger were seriously impaired, his wrist and long finger were partially impaired, and permanent neromas in his hand caused acute pain when triggered by contact. The result, according to Dr. Frey, was a permanent 50% disability of the left hand. Dr. Samuel Q. Mitchell also testified about his examinations of Martin and concluded that the functional impairment of Martin’s hand, together with the painful neromas, rendered Martin disabled from even limited duty.
Additional medical evidence came from various letters and reports written by Dr. Frey, Dr. Joseph D. Linehan, and the Board of Police and Fire Surgeons (Board of Surgeons). Dr. Linehan had examined Martin in 1984 and concluded that Martin’s wrist rendered him “incapable of light duty as a policeman.” In contrast, the Board of Surgeons, which reviews disability cases before they are heard by the Board, opined in its Summary Medical Report that Sergeant Martin, while “permanently disabled with a functional impairment of 20%,” could “perform limited duty.” The report was signed by Drs. Balkissoon and Chin-Lee, neither of whom had examined Martin at any time. It referred generally to “Martin’s medical history,” as well as to a 1984 report by Dr. Linehan which had concluded that Martin was incapable of light-duty po[105]*105lice work because he was able to use his left hand only as a “scoop.” The Board of Surgeons also relied on a report by the police department’s Internal Affairs Division which, as the surgeons interpreted it, tended to show that Martin could perform limited duty.
Non-medical evidence presented at the hearing concerned Martin’s musical and domestic activities. The Board admitted into evidence the report of the Internal Affairs Division cited by the Board of Surgeons. The investigations chronicled in this report were apparently aimed at gathering evidence, first, about whether Martin was working for pay while on sick leave and, second, about whether Martin used his left hand in ways incompatible with his claim for disability retirement. Internal Affairs gathered information by sending officers to watch Martin sing with a night club band and to interview Martin’s neighbors about how he used his left hand around the house. The report records the observations of five officers who watched Martin perform with the band; each reported various ways in which Martin used his left hand, such as to hold a microphone, push boxes, hold a glass, and grasp the hand of a woman with whom he danced. The report also states that one officer “observed a person whom he believed to be Sergeant Martin” pushing a power mower with both hands across the lawn of Martin’s house. Finally, the report summarizes statements by two neighbors who acknowledged they had seen Martin sometimes mow his lawn or shovel snow. A third neighbor made statements tending to exonerate Martin of the lawn-mowing charge; he had seen only Martin’s brother mowing the lawn for Martin. Neither the officers who elicited these statements nor the neighbors who spoke with the officers were called to testify at the hearing. Moreover, each of the neighbors had refused to sign written statements. The Internal Affairs Report was drafted by Sergeant Stanley E. Causey, the only officer of the five observers who testified at the hearing. The report was signed by Lieutenant Allen Smith, who had not participated in the observations or in the interviews of neighbors that are summarized in the report.
Martin was the final witness to testify. Based on his testimony, the Board established that Martin receives a salary of $33,-700 per year. Martin also described his light duty assignments during the ten weeks since returning to work in August 1985. He stated that he had conducted twenty interviews of job applicants, each taking about fifteen minutes; he had conducted a morning roll call twice a week, requiring about ten minutes each time; he had managed disbursements of money from a special fund, requiring an average of about three or four minutes; he had ensured that police cruisers belonging to his division received needed maintenance, occupying “a couple of minutes” a day; and he had signed leave slips, at thirty seconds each. Martin said that he senses he is “slighted” in the department because of the little work he does. He added that he feels he does not contribute to the department and his colleagues.
The Board concluded that Martin was not disabled from “useful and efficient service” with the police department. It relied on (1) Dr. Frey’s testimony that petitioner has full use of two fingers, partial use of two more, and some capacity to manipulate his thumb; (2) the Internal Affairs Report that Martin’s injury has not affected his “musical and away-from-the-department activities in which the left hand is used unre-strictedly and without apparent pain;” and (3) the conclusion of the Board of Surgeons that Martin is capable of light duty. The Board’s Decision ignores Dr. Mitchell’s testimony. Interestingly, moreover, in relying on Dr. Frey’s testimony, the Board expressly stated that Frey had “negate[d]” Dr. Linehan’s “characterization of the left hand as being useful mainly as a ‘scoop’ ” — a characterization which had supplied the only stated medical finding underlying the Board of Surgeons’ conclusion that Martin could perform limited duty. Finally, the Board’s decision makes no reference to the character of Martin’s current light duty assignments and contains no finding that Martin’s assigned work is “useful and efficient.”
[106]*106II.
In reviewing a decision of the Board, we may reverse only if its findings are unsupported by substantial evidence in the record or if the decision is grounded on a mistaken legal premise or manifests an abuse of discretion. See D.C.Code § l-1510(a)(3)(A) & (E) (1987 Replacement); Neer v. District of Columbia Police & Firemen’s Retirement & Relief Board, 415 A.2d 523, 525-26 (D.C.1980). Martin argues that, on the evidence presented at the October 1985 hearing, the Board erred as a matter of law in concluding he is able to perform “useful and efficient service in the grade or class of position” he occupied before receiving the injuries on his wrist.
A.
Because Martin was injured in the line of duty, he is entitled to disability retirement if his injury “permanently disables him for the performance of duty.” D.C.Code § 4-416(a) (1981) (stating disability retirement criteria for officers who became members of the force before February 15, 1980). To be “disabled” means to be “disabled [1] for useful and efficient service [2] in the grade or class of position last occupied.” Id. § 4-607(2). In Wells v. Police & Firefighter’s Retirement & Relief Board, 459 A.2d 136, 139 (D.C.1983) (en banc), we held that an officer seeking retirement bears the burden of establishing that he or she is disabled according to these statutory criteria.
In interpreting the second requirement of § 4-607(2) — i.e., for retirement, an applicant must be disabled for service “in the grade or class of position last occupied” —we have rejected the argument that an applicant is entitled to retire if disabled from performing his or her “old,” full-duty job. Seabolt v. Police & Firemen’s Retirement & Relief Board, 413 A.2d 908, 910-11 (D.C.1980). We have held, rather, that this statutory language broadly encompasses any of the jobs available to officers of the same rank and salary last held, and thus that retirement will be available only if the officer is incapable of performing any assigned light duty alternative to the previous job. See Wells, 459 A.2d at 138; Sea-bolt, 413 A.2d at 910-12. The “grade or class” requirement, therefore, places no meaningful restriction on the content of the jobs a partially disabled police officer may be required to perform. It merely ensures that an officer who is denied retirement may not suffer demotion and must be paid at his or her prior salary, whatever light duty job the officer is given. In the present case, Martin does not claim he has been demoted or now receives less than a full sergeant’s salary.
At issue here, therefore, is the first statutory requirement of § 4-607(2): for retirement, an applicant must be disabled from performing “useful and efficient service” within the department. This requirement governs the content of the job a partially disabled officer may be required to perform instead of being permitted to retire on disability. To date, however, this court has had little occasion to interpret what this requirement means, other than to make clear, as a general proposition, that light duty alternatives to the full duties a petitioner previously performed can constitute “useful and efficient service.” See, e.g., Wells, 459 A.2d at 138-39; Echard v. Police & Firemen’s Retirement & Relief Board, 422 A.2d 1275 (D.C.1980).
B.
The District urges that a department’s very willingness to retain a partially disabled employee at full salary is legally sufficient to show that he or she provides “useful and efficient service,” no matter what character or amount of work the employee actually performs. This argument is invalid.
First, the District’s interpretation would deprive the statute’s “useful and efficient service” language of all content, for it would allow the government to refuse to retire an employee who actually performed no work at all or whose job, while including some useful tasks, was obviously inefficient given the department’s needs, personnel, and budget. As long as the statute permits retirement only to those disabled from useful and efficient service, but gives [107]*107those who are so disabled the right to retire on disability, the Board must consider objectively, by reference to evidence, whether the petitioner is actually performing useful and efficient service justifying a full time salary.
Second, the District’s interpretation gives too great deference to the wishes of the departments in question. It is the members of the Board, not the heads of the police or fire departments, who determine whether a petitioner is eligible for disability retirement. Thus, in Jones v. Police & Firemen’s Retirement & Relief Board, 375 A.2d 1, 5-6 (D.C.1977), we held that internal police regulations eliminating the light duty alternative for officers injured off-duty did not control whether employees who were capable of light duty were disabled and eligible for retirement under the Police and Firefighters Disability Act. The same applies to specific retirement decisions: although the department’s needs and resources determine whether particular work is useful and efficient, and the department’s judgment on the question should be accorded appropriate weight, the Board must find for itself, based on evidence from the petitioner and the department alike, that the department actually provides useful and efficient work for each partially disabled employee before it denies retirement.
Finally, the District’s interpretation of “useful and efficient service” would provide no safeguard for disabled employees against overzealous application of the limits the law has placed on disability retirement. The rule that forbids disability retirement for employees who remain capable of delivering useful and efficient service prevents the waste and injustice of paying substantial annuities to persons who, although unable to perform the precise tasks they had undertaken before the injury or illness, can well perform different jobs in their departments. This rule, however, neither demands nor permits compelling partially disabled employees to assume artificial and substantially unproductive roles in their departments. Such application of the law would not only waste public funds but also demean disabled employees and subject them to the resentment of fellow workers. The requirement that disabled employees suffer no diminution of rank or salary itself serves to safeguard the dignity of employees disabled in the line of duty. Similiarly, requiring the Board to find that light duty work allotted to a partially disabled officer is in fact useful and efficient to the department will also help insure that the demands of the disability retirement law do not in practice add insult to injury for partially disabled police officers and firefighters.
C.
The District argues, alternatively, that, even assuming Martin’s current light duty tasks fail to satisfy statutory criteria for usefulness and efficiency, he has not met his burden under Wells to show there is no other “useful and efficient” job or aggregation of tasks that he could perform for the department. Apparently, the District believes that, even if the police department is not taking useful and efficient advantage of Martin’s limited capabilities, the Board’s decision to deny disability retirement should not be disturbed unless and until a petitioner shows there is no other sergeant’s work that he or she could perform if assigned. This approach suffers from three shortcomings.
First, there is no real difference between this argument and the contention, rejected earlier, that the District’s mere willingness to keep Martin employed at full salary satisfies the “useful and efficient service” requirement. We do not understand how Martin could be called materially more “useful and efficient” to the department if there were tasks he was able to do, but not assigned to, than if no such tasks were available.
Second, if an employee, such as Martin, were required to prove there was no other sergeant’s task that he could perform, it would be extremely difficult for that employee ever to meet the burden of proving that he cannot offer useful and efficient service to the department. The employee would have to negate a possibility, i.e., the [108]*108availability of other tasks, that only the department itself is in a position to resolve. For this reason, the court stated in Wells that, realistically, an applicant for disability retirement “will be able to show that no appropriate [light duty] job is available if the Department fails to place and keep him [or her] employed in such a job.” 459 A.2d at 139. This court thus recognized a feasible means by which a partially disabled employee could make a prima facie case, by reference to his or her own workload, that no “useful and efficient” work exists for one with his or her disability.
Third, the District’s approach would render virtually irrelevant as evidence the light duty work a petitioner’s department has seen fit to require; and yet, as the court recognized in Wells, the job a department has given a partially disabled employee is surely significant, if not conclusive, evidence of the work the department has available for a person with the particular capacities and disabilities of the employee in question.
D.
The “useful and efficient service” requirement probably admits of no universal and absolute criteria. In Wells and earlier cases, this court has stressed that one means of meeting a petitioner’s burden of establishing a disability that justifies retirement is to show that the department has failed to place and keep the petitioner in a job that he or she can perform in the grade or class of position last occupied. See id. at 139 & n. 3; Woody v. Police & Firemen’s Retirement & Relief Board, 441 A.2d 987, 989 (D.C.1982) (per curiam); Rzepecki v. Police & Firemen’s Retirement & Relief Board, 429 A.2d 1388, 1389, 1391 (D.C.1981) (Ferren, J., concurring). Similarly, the work a partially disabled employee has been given can be relevant evidence that the employee is disabled from “useful and efficient service.” Here, Martin attempted to show that the department had failed to place him in a useful and efficient position, and he presented evidence sufficient to raise the question whether the department had met its obligation to do so.
Martin has worked for ten weeks on light duty since returning from sick leave after his last operation. During that time the department has assigned to him a series of tasks that, according to his uncontradicted testimony, required in total about an hour to an hour and a half each week.1 Presumably, each of these tasks individually is necessary to the department, but Martin has clearly made a prima facie case that, taken together, these tasks do not add up to “useful and efficient” service for an employee paid a full-time salary. No representative of the police department appeared at the hearing to rebut Martin’s sworn testimony about the nature and duration of his assignments. Nor did anyone from the department attempt to demonstrate why such part-time tasks at a sergeant’s full pay were “useful and efficient” to the department. The Board, however, did not address the question raised by Martin’s testimony. Its failure to do so requires this court to reverse and remand for the Board to reach a determination as to whether Martin has been given work that amounts to “useful and efficient service” in light of the needs of the department and Martin’s physical capabilities. Inherent in this analysis is a consideration of the expense of keeping Martin on the force, given that the department cannot reduce his salary-
On remand, the department, if it opposes Martin’s disability retirement, may either (1) refute Martin’s testimony about the nature and time requirements of the work he has been given, or (2) present evidence sufficient to convince the Board that the duties Martin performs are nonetheless useful and efficient, or (3) show, on the basis of medical and other evidence, that [109]*109Martin could undertake more onerous, available tasks that he has been willing to try since his injury. The Board must take care, however, to ensure that whatever tasks the department proposes to give Martin are duties he can perform without significant discomfort or an exacerbation of his current disability.
III.
Martin claims the Board abused its discretion both by admitting into evidence the Summary Medical Report and the Internal Affairs Report and by barring his own introduction of a draft of the Summary Medical Report which Dr. Mitchell prepared but the Board of Surgeons rejected. We agree that the Summary Medical Report should not have been admitted into evidence, while portions of the Internal Affairs Report so lacked reliability as to indicate that the Board afforded them undue weight. We also agree that the Board unreasonably denied admission of the draft medical report.
Administrative hearings are not governed by the strict rules of evidence that regulate the flow of information at a court trial; thus, hearsay is generally admissible unless “irrelevant, immaterial, [or] unduly repetitious.” D.C.Code § l-1509(b) (1987 Replacement); see Jadallah v. District of Columbia Department of Employment Services, 476 A.2d 671, 676 (D.C.1984) (per curiam); Wallace v. District of Columbia Unemployment Compensation Board, 294 A.2d 177, 179 (D.C.1972). “Failure to apply these generous principles of admissibility can be a basis for reversal.” Kopff v. District of Columbia Alcoholic Beverage Control Board, 381 A.2d 1372, 1385 (D.C.1977); see also Committee For Washington’s Riverfront Parks v. Thompson, 451 A.2d 1177, 1184 (D.C.1982). On the other hand, the admission of hearsay evidence at administrative hearings must both satisfy a disability claimant’s constitutional right to due process and comport with common law restrictions designed to ensure that hearsay evidence does not undermine the accuracy of administrative adjudications. Reversal may be warranted if an agency places undue confidence in hearsay evidence that is too unreliable to justify the weight given to it. Jadallah, 476 A.2d at 676-77.
We turn, first, to the Summary Medical Report. In Richardson v. Perales, 402 U.S. 389, 91 S.Ct. 1420, 28 L.Ed.2d 842 (1971), the Supreme Court ruled that hearsay medical reports are admissible and may constitute substantial evidence at hearings to determine eligibility for federal Social Security disability benefits when they are sufficiently reliable and probative to comport with the requirements of procedural due process. The Court concluded that
a written report by a licensed physician who has examined the claimant and who sets forth in his report his medical findings in his area of competence may be received as evidence in a disability hearing and, despite its hearsay character and an absence of cross-examination, and despite the presence of opposing direct medical testimony and testimony by the claimant himself, may constitute substantial evidence supportive of a finding by the hearing examiner adverse to the claimant, when the claimant has not exercised his right to subpoena the reporting physician and thereby provide himself with the opportunity for cross-examination of the physician.2
[110]*110Perales, 402 U.S. at 402, 91 S.Ct. at 1427 (emphasis added). The Court stressed that its confidence in the reliability and probative value of the five medical reports at issue was derived from “a number of factors.” Id. For example, the reports were prepared by physicians who had personally examined the claimant; the reports reflected an “impressive range” of examination, as well as considerable detail in their findings and reasoning; and the reports were not inconsistent with one another. Id. at 402-04, 91 S.Ct. at 1427-28.
The due process analysis in Perales also governs the use of hearsay medical reports at disability hearings under the Police and Firefighters’ Disability Act, for the stakes and the medical issues are very much the same- as those for disability determinations under the Social Security Act. See id., at 390, 399-400, 91 S.Ct. at 1426-1427; Dowd v. District of Columbia Police & Firefighters’ Retirement & Relief Board, 485 A.2d 212, 215 (D.C.1984) (“the Perales holding is dispositive of the evidentiary issue raised by petitioner,” who had argued that written medical reports did not constitute substantial evidence in a disability retirement case).
Unlike the situation in Perales, the Board in the present case did not rely on the Summary Medical Report alone to supply the substantial evidence required to justify the Board’s factual conclusions. Although the Board’s decision states that the Board was “persuaded by the report of the Board of Police and Fire Surgeons,” the Board’s decision also describes at greater length certain of Dr. Frey’s detailed medical findings (to which the Board attributed an import substantially different from Dr. Frey’s own opinion in judging Martin’s disability under the statutory guidelines). We conclude, however, that a Perales analysis should govern the admissibility and weight of medical reports even when the Board does not rely solely upon a given document or set of documents for medical evidence adverse to the petitioner. We do so because medical reports purport to contain expert, scientific knowledge directly addressing central issues in a disability dispute. They are, therefore, particularly persuasive evidence in this context, and, when adverse, will inevitably prove highly prejudicial to a petitioner’s cause. Because hearsay medical reports purport to employ high professional standards of expertise, we must hold them, for purposes of admissibility, to a higher standard of reliability than we do other hearsay evidence.3
This case also differs from Perales in that the Summary Medical Report ostensibly reflects the collective judgment of a panel of physicians who have examined Martin’s medical records, whereas the re[111]*111ports in Perales were each the work of a single examining physician expressing his or her own judgment about a particular aspect of the claimant's health. Although we conclude that Perales governs the admissibility and weight justly accorded a document such as the Summary Medical Report, we do not believe that, to be admissible against a claimant at a disability hearing, an adverse medical report by a panel of doctors must always be drafted and signed by physicians who have personally examined the patient. The collective recommendation of a board of physicians helps to ensure the credibility and reliability of its conclusions, even though some or all members base their decisions on other doctors’ reports of examinations of the patient. On the other hand, we also believe that when a medical report has been prepared and approved by physicians who have not examined the subject of the report, due process requires, for admissibility, that those who issue the report must demonstrate that their conclusions about the nature and degree of a petitioner's disability were based upon information provided by an examining doctor.
Applying Perales to the present case, we conclude that introduction of the Board of Surgeon’s Summary Medical Report as evidence at Martin’s hearing did not meet the demands of due process. Not one of those who prepared, voted upon, or signed the report had personally examined Martin; each of the doctors who had examined Martin, including Dr. Linehan, to whom the report refers, concluded Martin was disabled from performing limited duty with the police. The only indication in the report itself of medical evidence to the contrary was Dr. Linehan’s reference to Martin’s ability to use his hand as a “scoop,” a characterization which, ironically, the Retirement Board itself found necessary to “negate” by reference to Dr. Frey’s testimony. Moreover, the Board of Surgeons, in reaching its recommendation, relied in part on the Internal Affairs report which, as elaborated below, we conclude was afforded undue weight. It is true that Dr. Mitchell, a member of the Board of Surgeons who had examined Martin, had written a draft of the Report. But he was on leave when Martin’s case came before the Board of Surgeons, and his draft was rejected or ignored in the preparation of the final report. When asked whether the Summary Medical Report was his report on Martin’s condition, Dr. Mitchell clearly stated “No it is not,” and when asked whether he was part of the committee that submitted the report, he stated that he was not. (Despite all this, Dr. Balkissoon purported to sign the report for Dr. Mitchell.)
In sum, the fatal defect in the Summary Medical Report is its conclusory character. The Report contains only one paragraph of medical analysis of Martin’s condition. This paragraph consists of a substantial quotation from a report submitted by Dr. Linehan, who had examined Martin in 1984. But in the passages quoted, Dr. Linehan states in some detail his reasons for concluding that Martin was disabled from performing limited duty in the police force. The Report then states that, the Board of Surgeons having reviewed Martin’s medical history and the Internal Affairs Report, “it was their decision that Sergeant Martin could perform light duty.” That was all. In a document that purports to reflect the considered judgment of medical experts about a man’s medical condition we see no medical findings or reasoning supporting the conclusion that Martin could perform limited duty. Such hearsay evidence so lacks the indicia of reliability enunciated in Perales that its use by the Board deprived Martin of due process of law.
Introduction of the Internal Affairs Report does not raise such acute questions of due process as did use of the Summary Medical Report, for the Internal Affairs Report did not purport to reflect an expert, technical evaluation of Martin’s condition. Moreover, it reported, if indirectly, the statements of persons who claimed to have personally observed the events related in it. But, because hearsay presents special dangers to the accuracy of findings based on such evidence, our cases indicate that an administrative board must carefully exam[112]*112ine the reliability of the hearsay it proposes to consider in order to determine how much weight the evidence may properly receive. Hearsay may constitute substantial evidence only when shown reliable and credible, see, e.g., Simmons v. Police & Firefighters’ Retirement & Relief Board, 478 A.2d 1093, 1095 (D.C.1984), and, at least without clear indicia of reliability, “hearsay evidence alone should not be permitted to offset the sworn testimony of a wit-ness_” Jadallah, 476 A.2d at 677 (Fer-ren, J., concurring). In the extreme case, hearsay may appear so unreliable that it is “of little, if any, probative value.” Id. at 677.
On the premise that Sergeant Causey drafted the Internal Affairs Report, we note it contained evidence that for present purposes falls into three classes: Sergeant Causey’s own observations; those of other police officers whose reports Sergeant Cau-sey summarized in the Internal Affairs Report; and observations reported by Martin’s neighbors to police officers and subsequently related to Sergeant Causey for his report. We have no difficulty with admission of the first class of observations, for the identity between the witness and the author of the report, together with Sergeant Causey’s presence at the hearing for questioning, lent his observations significant indicia of reliability. While the other two classes of observations were technically admissible, their probative value is limited. The second class of observations comprised hearsay within hearsay, since Sergeant Causey summarized in his report what other witnesses had told him. The third class of observations arose from an even more problematic chain of communication. These observations were triple hearsay, originating with the neighbors interviewed, then passed to the interviewing officers, then to Sergeant Causey for his report to the Board. We have previously criticized the use of hearsay within hearsay as grounds for decision, for reliance upon such an “attenuated evidentiary chain” seriously compromises the trustworthiness of the final decision. See Jadallah, 476 A.2d at 677.
The weakness of such evidence is demonstrated by the allegations reported in the Internal Affairs Report, many of which are imprecise or unsure and, as a result, of only the most questionable probative value for the issue at stake: Martin’s capacity for useful and efficient service in the police department. For example, officers who watched Martin performing with his band are said to have reported that he “extensively used his left hand,” held the mike cord in his left hand with his thumb and index finger,” “handled and closed up two brief case style containers using both hands,” and “handled drinks.” Since Martin has not claimed that his left hand is totally disabled from use, such statements, though clearly prejudicial in appearance, would require careful examination and honing to become trustworty gauges of Martin’s ability to perform the rather different tasks characteristic of the police station. (There is no evidence that Martin has been offered a job to sing for the police department.)
The statements about Martin’s domestic activities are even more questionable. One officer is said to have “observed a person whom he believed to be Sergeant Martin” pushing a mower across his front lawn; a neighbor is said to have seen Martin “cutting grass” while exhibiting no physical disabilities “to a casual observer.” The Board learned nothing of why the officer thought it was Martin he saw, or of what it meant to the neighbor to say that one is “cutting grass,” or of the circumstances under which these observations were made. At the disability hearing, Martin himself challenged the truth or meaning of many of the Report’s assertions about his use of his left hand. The Board had no opportunity to test the bias or certainty of those whose statements Martin challenged. For these reasons, and in light of the legal standard we have established, we conclude that, except as to Sergeant Causey’s own personal observations, the Board should not have placed much confidence in the Internal Affairs Report as a measure of Martin’s disability for “useful and efficient service.”
[113]*113c.
At the hearing, petitioner sought to introduce the draft summary medical report that Dr. Mitchell had prepared for the Board of Surgeons before going on leave and to examine Dr. Mitchell about the contents of this draft. Dr. Mitchell testified at the hearing that in his judgment Martin was disabled from useful and efficient service. Dr. Mitchell’s draft reflected his opinion. Martin wanted to undermine the credibility of the Summary Medical Report by showing that the one member of the Board of Surgeons who had personally examined Martin differed with the Board of Surgeons’ judgment on Martin’s degree of disability and on the ultimate question of his ability to perform limited duty for the police department. The Board denied admission of the draft report and precluded Martin from questioning Dr. Mitchell about its contents.
Martin claims that the Board unjustly blocked his effort to impugn the credibility of the Summary Medical Report — itself hearsay that the Board admitted into evidence — with Dr. Mitchell’s draft report. We agree. Indeed, when the reliability of the two hearsay documents is considered, Dr. Mitchell’s draft would appear in two respects to have been the more reliable of the two reports, for it was prepared by a doctor who had examined the patients, cf. Perales, 402 U.S. at 402-03, 91 S.Ct. at 1427-28, and its author was present to answer questions regarding its contents. In these ways, Dr. Mitchell’s draft report was like Sergeant Causey’s own observations that we held admissible from the Internal Affairs Report. Moreover, the applicable statute and our cases make clear a strong preference for admitting relevant evidence, including reliable hearsay, at an administrative hearing. See D.C.Code § l-1059(b) (1987 Replacement); Thompson, 451 A.2d at 1184; Kopff, 381 A.2d at 1385.
IV.
We remand for the Board to determine whether Martin’s disability prevents him from performing service that is “useful and efficient.” The Board may hold a new hearing to allow additional evidence from the police department, the Board of Surgeons, or Martin. In any case, the Board should reach an independent judgment, based on the record evidence of Martin’s physical capabilities, the department’s needs, the work Martin has been given since his disability, and other tasks to which he could be assigned without pain or aggravation of his condition. Inherent in this analysis is consideration of the cost of continuing to employ Martin as a full-time sergeant.4
So ordered.