CHIEF JUSTICE CARRICO
delivered the opinion of the Court.
In the first phase of a bifurcated trial conducted pursuant to Code §§ 19.2-264.3 and -264.4, a jury convicted Michael Charles Satcher of the robbery, assault and battery, and attempted rape of Deborah Abel and the robbery, rape, and capital murder of Ann Elizabeth Borghesani.1 The jury fixed Satcher’s punishment at imprisonment for life plus ten years and twelve months for the offenses against Ms. Abel and at two terms of life imprisonment for the noncapital offenses against Ms. Borghesani. In the second phase of the trial, the jury fixed Satcher’s punishment for the killing of Ann Borghesani at death, based upon both statutory predicates of “future dangerousness” and “vileness.”
After considering a postsentence report prepared by a probation officer, Code § 19.2-264.5, the trial court imposed the sentences fixed by the jury. Satcher is here for automatic review of his death sentence, and we have consolidated that review with his appeal of his capital murder conviction. Code § 17-110.1. We have also certified from the Court of Appeals Satcher’s convictions for the offenses against Ms. Abel and the noncapital offenses against Ms. Borghesani. Code § 17-116.06. We have given the entire matter priority on our docket. Code § 17-110.2.
FACTS
The incidents involving Ms. Abel and Ms. Borghesani both occurred on March 31, 1990, on a bicycle path that runs alongside Lee Highway, past the Air Force Association building, in the Rosslyn section of Arlington County. The bicycle path at this location is hidden from the view of motorists and pedestrians proceeding along Lee Highway by a “sound barrier wall” some fifteen to twenty feet in height.
Shortly before 7:00 p.m. on March 31, Ms. Abel was riding her bicycle along the path and had just passed the Air Force Association [226] building when she saw a man walking toward her. As they passed one another, they “made eye contact.” The next thing she knew, she was pulled off her bicycle, dragged on her stomach into a ditch that ran alongside the bicycle path, and “jumped on from behind.” Every time Ms. Abel turned her head to plead with her assailant or to get a look at him, he would hit her in the head and face. She told him there was money in her purse and begged him to “go get that” and not “hit [her] anymore.” As he continued to beat her, he managed to get her “pants part way down.”
Suddenly, Ms. Abel’s assailant “stopped what he was doing.” It turned out that another cyclist, Mark Polemani, happened to pedal past the scene and saw a mountain bike “off the bike trail.” He also observed a man kneeling down “right off the path,” and when he saw the man “throw a punch to the ground,” he stopped and got off his bicycle. When the man saw Polemani, he picked up Ms. Abel’s purse and ran. Polemani pursued him, but he escaped.
Polemani returned to the scene to retrieve his bicycle and, for the first time, saw Ms. Abel. Her face and her sweatshirt were covered with blood and her “pants and her panties were down at her ankles.” He walked with her to an apartment complex and knocked on a door. The police were called, and Ms. Abel was transported to a hospital. Several days later, her purse was found at a nearby parking lot. It contained her personal belongings, but no money.
At 8:00 p.m. on the same evening, Ann Borghesani was to be the guest of honor at a belated birthday party given for her by a friend who lived in the Crystal City area of Arlington County. Ms. Borghesani lived in an apartment at Rosslyn. From her apartment, it was about a five minute walk along the bicycle path, past the Air Force Association building, to a Metro station, where Ms. Borghesani could have taken a train to Crystal City.
Ms. Borghesani was last seen alive about 7:10 p.m. by her roommate, Susan Cohen. As Ms. Cohen left the apartment to go to dinner with her fiance, Ms. Borghesani was ironing some clothes.
Ms. Borghesani never appeared at the birthday party. When she failed to appear, her friends instigated a search, and, when they could not find her, they called the police.
Ms. Borghesani’s body was found the next morning at the bottom of a stairwell of the Air Force Association building. She was nude “from her midsection down,” she had been raped, and her body bore multiple wounds, many inflicted with a weapon having a sharp-tipped blade. Her rings were missing, and earrings “she was [227] wearing [the night before] had been ripped from her ears.” One of her shoes was found on the bicycle path. Later that day, her purse was found at the same parking lot where Deborah Abel’s purse was found and, like Ms. Abel’s, it contained no money.
On August 18, 1990, four and one-half months after the Borghesani murder, Satcher was observed on another bicycle path in Arlington County. He was arrested for offenses he had committed that day. Nothing was said to him concerning the Borghesani rape and murder, but, as he was being transported to police headquarters, he told an officer that the police were ‘ ‘trying to frame [him] for a murder or something or a rape or something.”
In the glove compartment of Satcher’s car, police found an awl.2 Satcher admitted he owned the awl on the date of the murder. In the medical examiner’s opinion, the awl was “consistent with [Ann Borghesani’s] wounds.” Scientific tests matched semen removed from Ms. Borghesani’s body with blood taken from Satcher.
ISSUES PREVIOUSLY RESOLVED
In a motion filed below, Satcher sought to “prohibit the imposition of the death penalty against him on the grounds that the Virginia death penalty statutes [violate] the Sixth, Eighth and Fourteenth Amendments of the United States Constitution and Sections Eight, Nine and Eleven of the Constitution of Virginia.” The trial court denied the motion, and Satcher assigns the denial as error.
All the arguments Satcher makes on appeal in support of the motion have been answered by previous decisions of this Court. He has not advanced sufficient reason to justify a departure from the views previously expressed, and we can perceive of none. Accordingly, we will reaffirm our earlier decisions and reject Satcher’s arguments. The arguments Satcher makes and the decisions answering them are as follows:
A. Virginia’s “vileness” predicate for imposition of the death penalty is unconstitutionally vague as applied and the “future dangerousness” predicate is unreliable and vague because the jury’s discretion is not limited or guided in any way. Answered by M. Smith v. Commonwealth, 219 Va. 455, 476-78, 248 S.E.2d 135, 148-49 (1978), cert. denied, 441 U.S. 967 (1979).
[228] B. Due process is violated by the use of evidence of unadjudicated acts of misconduct to prove “future dangerousness” without an instruction requiring proof of such acts beyond a reasonable doubt. Answered by Stockton v. Commonwealth, 241 Va. 192, 210, 402 S.E.2d 196, 206, cert. denied, 502 U.S. _, 112 S.Ct. 280 (1991).3
C. The death penalty is imposed arbitrarily and discriminatorily where, as in this case, the victim is white and the defendant is black. Answered by Townes v. Commonwealth, 234 Va. 307, 335, 362 S.E.2d 650, 666 (1987), cert. denied, 485 U.S. 971 (1988).
D. The death penalty is excessive and repugnant to society’s evolving standards of decency and, hence, is violative of the Eighth Amendment’s prohibition against cruel and unusual punishment. Answered by M. Smith, 219 Va. at 476, 248 S.E.2d at 148.
E. The manner in which the jury receives evidence and instructions on the subject of mitigation is constitutionally improper. Answered by Watkins v. Commonwealth, 229 Va. 469, 490-91, 331 S.E.2d 422, 438 (1985), cert. denied, 475 U.S. 1099 (1986).
F. The death penalty statutes are unconstitutional as applied because a defendant cannot secure either a meaningful appellate review of the predicates of “vileness” and “future dangerousness” or an objective determination whether his sentence is the product of passion and prejudice or is disproportionate to the penalty imposed in similar cases. Answered by R. Smith v. Commonwealth, 239 Va. 243, 253, 389 S.E.2d 871, 876, cert. denied, 498 U.S. 882 (1990).4
PRETRIAL MATTERS
Motion for Separate Trials
By pretrial motion, Satcher sought separate trials of the offenses involving Deborah Abel and those involving Ann Borghesani. After [229] argument, the trial court denied the motion. Satcher assigns the denial as error.
As pertinent here, Rule 3A: 10(b) provides that all offenses pending against an accused may be tried at one time ‘ ‘if justice does not require separate trials and . . . the offenses meet the requirements of Rule 3A:6(b).” Under Rule 3A:6(b), joinder of offenses is permissible if they “are based on the same act or transaction, or on two or more acts or transactions that are connected or constitute parts of a common scheme or plan.”
Satcher argues that the “interests of justice required separate trials because identity was the key issue in both cases” and consolidation “allowed the Commonwealth to take weak identity evidence from two cases in an effort to identify [him] although there was no evidence that the same assailant attacked both women.” Furthermore, Satcher says, “the offenses were not connected or part of a common scheme or plan.” Hence, Satcher concludes, the denial of his motion for separate trials constituted a violation of Rules 3A: 10(b) and 3A:6(b).
We disagree with Satcher. From the evidence and the reasonable inferences to be drawn therefrom, it is clear that the two or more acts involved in this case constituted parts of a common scheme or plan and were closely connected in time, place, and means of commission, all of which supports the use of a single trial. The two crimes occurred within a few yards and about one-half hour of each other. Both victims were forcibly removed from the bicycle path at a location concealed behind the “sound barrier wall.” In each instance, the victim was brutally beaten and partially disrobed. The criminal intent of the assailant — to commit rape and robbery — was the same in both situations. The purse of each victim was stolen, and the two purses were found in approximately the same location, with only money missing from both.
Hence, the requirements for a single trial under Rule 3A:6(b) are satisfied in this case. And, contrary to Satcher’s argument that consolidation “allowed the Commonwealth to take weak identity evidence from two cases in an effort to identify [him],” the evidence, as we will demonstrate infra, established Satcher as the assailant in both cases with a high degree of certainty. Therefore, Satcher’s Rule 3A: 10(b) “interests of justice” argument does not stand up. Indeed, on balance, the interests of justice favored trying all the offenses against Satcher in a single trial.
[230] Furthermore, Satcher’s separate-trial argument is based solely upon the trial court’s alleged error in the application of Rules 3A:10(b) and 3A:6(b). However, “[a]n error ... in the application or interpretation of a Rule of Court will not constitute reversible error unless the substantive rights of a party have been affected.” Foster v. Commonwealth, 6 Va. App. 313, 323, 369 S.E.2d 688, 694 (1988) (citing Rule 3A:2(a)).5 Hence, misapplication of Rules 3A: 10(b) and 3A:6(b) would not constitute reversible error unless the misapplication affected Satcher’s substantive rights. And, as we decide infra, Satcher’s substantive rights would not have been affected because, in a separate trial of Ann Borgehsani’s murder, evidence of the offenses involving Deborah Abel would have been admissible.
Generally, evidence of other offenses is inadmissible in a criminal prosecution, but there are well-established exceptions. “[Ejvidence of similar acts is admissible to show a common scheme, design, or plan where there is‘such a concurrence of common features that the various acts are naturally to be explained as caused by a general plan of which they are the individual manifestations.’” McWhorter v. Commonwealth, 191 Va. 857, 870-71, 63 S.E.2d 20, 26 (1951) (citations omitted).
Evidence of other offenses is admitted if it shows the conduct and feeling of the accused toward his victim ... or if it tends to prove any relevant element of the offense charged. Such evidence is permissible in cases where the motive, intent or knowledge of the accused is involved, or where the evidence is connected with or leads up to the offense for which the accused is on trial. Also, testimony of other crimes is admissible where the other crimes constitute a part of the general scheme of which the crime charged is a part.
Kirkpatrick v. Commonwealth, 211 Va. 269, 272, 176 S.E.2d 802, 805 (1970).
“Evidence of other crimes is admissible when it tends to establish a common plan, design, or scheme embracing a series of crimes, including the crime charged, so related to each other that [231] proof of one tends to prove the other.” Charles E. Torcía, Wharton’s Criminal Evidence § 186 (14th ed. 1985). However, for such evidence to be admissible, its probative value must outweigh its prejudicial effect. Coe v. Commonwealth, 231 Va. 83, 87, 340 S.E.2d 820, 823 (1986).
Guided by the standards set forth in McWhorter, Kirkpatrick, and Wharton, we think that the evidence of the Abel offenses would have been, admissible in a separate trial of Ann Borghesani’s murder and that, compatible with Coe, the probative value of such evidence would have outweighed its prejudicial effect. Hence, Satcher’s substantive rights were not affected by the trial court’s application of Rules 3A: 10(b) and 3A:6(b) in its decision to deny separate trials, and no reversible error resulted from that decision.
In the final analysis, “[wjhether different offenses should be tried separately is a matter that rests within the sound discretion of a trial court.” Cheng v. Commonwealth, 240 Va. 26, 33, 393 S.E.2d 599, 603 (1990). We hold that the trial court did not abuse its discretion in denying Satcher’s motion for separate trials.6
Motion for Bill of Particulars
Satcher filed a motion for a bill of particulars, listing ten items upon which information was desired concerning the offenses involving Deborah Abel. Satcher asserted in the motion that the indictments returned against him did not “inform [him] of the cause and nature of the offenses with which he [was] charged.”
The Commonwealth responded voluntarily by filing a bill of particulars covering five of the items upon which information was requested. The trial court denied the motion with respect to the five remaining items. Satcher contends the trial court erred.
We disagree with Satcher. An indictment is sufficient if it gives the accused “notice of the nature and character of the offense charged so he can make his defense.” Wilder v. Commonwealth, 217 Va. 145, 147, 225 S.E.2d 411, 413 (1976). Where, as here, an indictment meets that standard, a bill of particulars is not required. Ward v. Commonwealth, 205 Va. 564, 569, 138 S.E.2d 293, 296-97 [232] (1964); Tasker v. Commonwealth, 202 Va. 1019, 1024, 121 S.E.2d 459, 462-63 (1961). Strickler, 241 Va. at 490, 404 S.E.2d at 233.
Motion for Discovery
Satcher also filed a motion for discovery concerning the offenses involving Deborah Abel. In Paragraph 13 of the motion, Satcher sought certain information, “pursuant to the rulings in Brady v. Maryland[, 373 U.S. 83 (1963)].” The trial court denied the motion with respect to items (d), (e), and (f) of Paragraph 13, and these three items are subjects of an assignment of error.
In item (d), Satcher requested “descriptions provided by any witness [differing] from the physical characteristics of the Defendant.” During argument below, the prosecutor represented that, pursuant to an “open file discovery” policy his office was observing in the case, he had furnished Satcher “all descriptions that were given of the defendant.” Upon the strength of this representation, the trial court denied item (d). We find no error in this action of the trial court.
In items (e) and (f), Satcher requested “any statement or action by any witness ... indicating that such witness was unable to identify [or was uncertain about his or her identification of] the Defendant as the perpetrator of these offenses.” Agreeing with the prosecutor that the information requested in items (e) and (f) would be exculpatory “only if the witness [thought] it was somebody [other than Satcher who committed the offenses],” the trial court denied items (e) and (f). We find no error in this action of the trial court and no Brady violation with respect to any of the information sought by Satcher in items (d), (e), and (f).
GUILT PHASE
Jury Selection
Voir Dire Examination
Satcher contends that the trial court erred in refusing to ask prospective jurors the following question:
[I]f we have a situation in which a young woman is raped, robbed by a person armed with a deadly weapon, stabbed [233] twenty-one times, beaten and murdered,... in that type of situation do any of you believe that the imposition of the death penalty would be the most appropriate sentence?
In Patterson v. Commonwealth, 222 Va. 653, 657, 283 S.E.2d 212, 214 (1981), defense counsel proposed asking prospective jurors whether they believed “that the death penalty is ordinarily the proper punishment for the crime of capital murder.” And in Buchanan v. Commonwealth, 238 Va. 389, 402, 384 S.E.2d 757, 764 (1989), cert. denied, 493 U.S. 1063 (1990), the question proposed was whether prospective jurors believed “that a death sentence is the only appropriate punishment for capital murder.” We approved the rejection of both questions. The question proposed here is nearly identical, and we approve its rejection.7 See Mueller v. Commonwealth, 244 Va. 386, 400, 422 S.E.2d 380, 386 (1992).
DNA Bias
Satcher contends the trial court erred in refusing to strike for cause prospective jurors “who had preconceived opinions concerning the reliability of DNA evidence.” The refusal to strike these prospective jurors, Satcher says, shifted the burden of proof to the defense.
On voir dire examination, Earl Barbee stated that he thought DNA was “sort of like a fingerprint” and “would be pretty accurate.” Robert Goldman and Bruce Walch said that they were convinced DNA is a reliable form of identification and would have to be convinced of its unreliability. William Gay stated that DNA “is the same as a fingerprint” and that he would have to be convinced it was not a reliable means of identification.
We do not think that the trial court erred in refusing to strike these prospective jurors for cause. As the prosecutor observed during argument on Satcher’s motion to strike prospective juror Bar-bee: “People do not come into juries totally with blank minds. They must come in with some knowledge.”
[234] As will be demonstrated infra in the section of this opinion entitled Admissibility of DNA Evidence, both this Court and the General Assembly of Virginia have considered the question whether DNA is a reliable means of identification and both have settled the question in favor of reliability. In stating that they considered DNA evidence reliable, the prospective jurors merely displayed knowledge of a conclusion that is part of the established law of this Commonwealth. Hence, their possession of such knowledge did not disqualify them from service on the jury.
Predisposition to Death Penalty
Prospective jurors were examined on voir dire in groups of four. Defense counsel asked the members of each group the same general question, viz., whether a person who is found guilty of the type of offense with which Satcher was charged should receive the death penalty. Satcher contends that the trial court erred in refusing to strike for cause five prospective jurors, Earl Barbee, Agnes Sulak, Robert Goldman, Angela Lawson, and Ronald Tuttle.8 Satcher says that all five indicated a predisposition toward imposition of the death penalty.
Prospective juror Barbee said “it depends on the circumstances,” whether, for example, the accused had committed murder more than once, and he indicated that, under such circumstances, the defense would have to convince him that the death penalty should not be imposed. Such circumstances did not exist, of course, in Satcher’s case. Barbee also said that the Commonwealth would have to prove to him that “the crime was so gruesome that it would require the death penalty.”
Prospective juror Sulak stated that she agreed with another prospective juror, one not challenged by Satcher, who said that she was “[n]ot necessarily” disposed toward imposing the death penalty. [235] When pressed by defense counsel to say whether she was predisposed, Sulak replied that “[i]t would depend.”
Prospective juror Goldman stated that, considering the facts in Satcher’s case as detailed by defense counsel, he would have to be given “some other factors to convince [him] that the death penalty should not be imposed.” But Goldman indicated he did not believe that “every person who has been convicted of murder should receive the death penalty.” And when asked whether he would be “predisposed towards imposing the death penalty” under the facts of Satcher’s case, he said “[i]t depends on the facts.”
Prospective juror Tuttle said “[i]t depends on the instructions that the Judge would give, what were the guidelines in the law.” He stated further that “if [the death penalty is] deserved, yes[, he] would impose [it],” but his opinion was not so strong that he would carry “a picket sign” in front of the courthouse. And he said it was not his belief that the death penalty was ‘ ‘the only appropriate punishment.”
Prospective juror Lawson said “[i]t depends on the situation.” When asked by defense counsel whether, in cases like Satcher’s, she would be “predisposed towards imposing the death penalty,” she replied in the affirmative. But she immediately indicated she would have no difficulty in deciding that life imprisonment was the appropriate punishment in “any type of murder.”
Indeed, in making this latter commitment, Lawson joined the other four prospective jurors in question, who also indicated that they would have no difficulty in deciding that life imprisonment was an appropriate punishment in any type of murder. And all five prospective jurors indicated that they could consider evidence in mitigation, that is, evidence used to convince them that death is not the appropriate punishment.
In addition, all five prospective jurors indicated that their views concerning the death penalty would not affect their ability to render an impartial verdict on the issue of guilt or innocence. All five indicated that, if the jury found Satcher guilty, they could follow the court’s instructions concerning the necessity for the Commonwealth to prove the aggravating factors of “future dangerousness” or “vileness” before the death penalty could be imposed. All five indicated that they were unaware of “anything at all” which would affect their ability to render a fair and impartial verdict on the issue of guilt or innocence.
[236] Furthermore, all five prefaced their views about imposition of the death penalty with the cautionary expression, “it depends.” And, with respect to all five, the trial court expressed confidence in their ability to follow the court’s instructions, to stand indifferent to the cause, and to render a fair verdict.
As an appellate court, we must give deference to the trial court’s decision whether to retain or exclude individual veniremen because the trial court “sees and hears the juror.” Wainwright v. Witt, 469 U.S. 412, 426 (1985); accord Spencer v. Commonwealth, 238 Va. 563, 572, 385 S.E.2d 850, 855 (1989), cert. denied, 493 U.S. [1093], 110 S.Ct. 1171 (1990) (Spencer III); O’Dell v. Commonwealth, 234 Va. 672, 693, 364 S.E.2d 491, 503, cert. denied, 488 U.S. 871 (1988). For that reason, the trial court’s decision in that regard will not be disturbed on appeal absent a showing of “manifest error.” Spencer IV, 240 Va. at 94, 393 S.E.2d at 619.
The standard to be applied by the trial court in determining whether to retain a venireman on the jury panel is whether his answers during voir dire examination indicate to the court something that “would prevent or substantially impair the performance of his duties as a juror in accordance with his instructions and his oath.” Adams v. Texas, 448 U.S. 38, 45 (1980); accord Turner v. Commonwealth, 234 Va. 543, 549, 364 S.E.2d 483, 486, cert. denied, 486 U.S. 1017 (1988); O’Dell, 234 Va. at 695, 364 S.E.2d at 504.
Eaton v. Commonwealth, 240 Va. 236, 246, 397 S.E.2d 385, 391 (1990), cert. denied, 502 U.S._, 112 S.Ct. 88 (1991).
We discern nothing in the record to indicate that the trial court failed to observe this standard in deciding that the five prospective jurors were not predisposed toward imposing the death penalty; indeed, “[t]he record gives every indication that [before reaching a decision] the trial judge gave close and conscientious attention to the demeanor of the veniremen.” Spencer IV, 240 Va. at 94, 393 S.E.2d at 618. We cannot say, therefore, that there is manifest error in the trial court’s decision to retain the five veniremen.
[237] Prospective Juror Middle
Herbert Middle stated on voir dire that his son-in-law was an Arlington County policeman and that he was friendly with other county police officers. Initially, Middle admitted “[i]t’s a possibility” that his relationship with police officers “might cause [him] to give more weight to their testimony than [he] might give to someone that [he did not] know,” and he asked to be excused from service on the jury.
Middle indicated, however, that he had not discussed Satcher’s case with his son-in-law and had not reached an opinion concerning Satcher’s guilt or innocence. Middle said he “would have to weigh [the testimony of police officers] for [himself] and find out [who was giving the accurate testimony].” He also said he would “weigh the facts of both sides,” and he responded affirmatively to the trial judge’s question whether he would “make [his] decision based on [the evidence]; not because [he] may or may not know somebody.” He also responded “[r]ight” to the judge’s question whether he could “stand indifferent to this cause.” Under these circumstances, we cannot say there is manifest error in the trial court’s refusal to strike Middle for cause.
Prospective Juror Oppenheimer
The trial court dismissed Michelle Oppenheimer as a prospective juror because she stated on voir dire that she “could not honestly take [the] oath [as a juror] if ... it would require [her] to support the death penalty.” Satcher contends the court’s action “constituted a violation of [his] right to a fair and impartial jury.”
We disagree with Satcher. Ms. Oppenheimer clearly indicated that her “views‘would prevent or substantially impair the performance of [her] duties as a juror in accordance with [her] instructions and [her] oath.’” O’Dell, 234 Va. at 695, 364 S.E.2d at 504 (quoting Adams v. Texas, 448 U.S. 38, 45 (1980)). Accordingly, the trial court did not err in dismissing Ms. Oppenheimer.
Alternate Jurors
Before jury selection began, the trial court and counsel agreed that twenty-four persons would be empaneled, from which each side would strike five, and that the remaining fourteen would hear all the [238] evidence. It was further agreed that when both sides had rested, two jurors would be excused, leaving twelve to deliberate. The trial court ruled that the two jurors to be excused would be selected at random.
On the first day of trial, before the jurors were sworn, one of the fourteen became ill and was excused. The trial court ruled that the trial should proceed and that, when the evidence was concluded but before deliberations began, one juror, to be selected at random, would be excused. Satcher then moved to strike the entire panel and to select a new one. The trial court denied the motion, finding that “any further delay at this point is unreasonable and unnecessary.”
Satcher asserts that the defense exercised its peremptory challenges in reliance upon the participation of a panel of fourteen. He argues that, when the ill juror was excused, 1 ‘the trial court abused its discretion by not allowing the defense to either . . . add another juror through a separate voir dire procedure . . . or . . . dismiss the jury and allow the parties to choose another fourteen.” Satcher concludes that the trial court’s action “violated the spirit of Swain v. Alabama, 380 U.S. 202 (1965) ‘which cautions that the right to one’s peremptory challenges shall not be impaired.’”
We disagree with Satcher. He does not question the trial court’s action in excusing the ill juror. And, as he acknowledges, the manner of proceeding under the circumstances was a matter for the exercise of the trial court’s discretion. We cannot perceive of any prejudice Satcher may have suffered from the trial court’s action, and we are unable to find any abuse of discretion on the court’s part. Hence, we reject Satcher’s argument on the subject.
DNA Evidence
Reliability
Semen removed from the body of Ann Borghesani and a sample of Satcher’s blood were subjected to DNA analysis. DNA is an abbreviation for the term deoxyribonucleic acid.
DNA, the active substance of the genes, carries the coded messages of heredity in every living thing: animals, plants, bacteria, and other microorganisms. In humans, the code-carrying DNA occurs in all cells that have a nucleus, including [239] white blood cells, sperm, cells surrounding hair roots, and cells in saliva.
Human genes are carried in 23 pairs of chromosomes, long threadlike or rodlike structures that are a person’s archive of heredity. Those 23 pairs [are] the total genetic makeup of a person ....
National Research Council, DNA Technology in Forensic Science S-l (1992).
Except for identical twins, the DNA of a person is for practical purposes unique. That is because one chromosome of each pair comes from the father and one from the mother ....
Id. at S-2.
Testimony adduced below showed that chromosomes are composed in part of DNA molecules. In DNA “printing” or “typing,” DNA molecules are chemically extracted from biological specimens such as semen or blood. The molecules are subjected to a procedure using “restriction enzymes,” which “cut the DNA” and produce ‘ ‘hundreds and hundreds of [DNA] fragments that are . .. all different sizes.”
The next step is known as electrophoresis, which employs a medium “very similar to Jello in nature” and which separates and arranges the different sized fragments according to their lengths. A nylon membrane is then placed over the Jello-like medium and the DNA fragments “actually migrate” into the membrane, after which chemicals transform “the double-stranded DNA molecule . . . into a single-stranded molecule.”
Next, a DNA “probe,” which is “a short section of single-stranded DNA” with radioactive material attached to it, is applied to the fragments. The probe “look[s] across all the hundreds of different fragments . . . and attach[es] itself to [a particular] fragment.” The membrane is put in contact with x-ray film, resulting in a band or bands representing the spot where light was given off when the probe attached itself to the fragment. Any excess probe is washed off, and an autoradiogram, or autorad, is produced.
The autorads are examined, and a comparison is then made of the banding patterns of a sample of body fluid found at a crime scene [240] with the patterns of a specimen extracted from a suspect. Four different probes are used to determine, for example, whether a semen sample found on the clothing of a rape victim matches the blood of a particular suspect. A match occurs when the bands of the two specimens are in the same position.
If a match is found, the next step is to determine “how often is this particular pattern seen in the Caucasian population and how often is it seen in the black population.” This determination is made for each of the four probes that are performed, and then “an overall profile frequency” is calculated. The purpose of the exercise is to eliminate large parts of the population until all the probes are exhausted and a determination can be made of ‘ ‘how likely is it to see someone with a pattern that matches this particular [specimen].”
Richard A. Guerrieri, a forensic serologist employed by the Commonwealth at the Tidewater Regional Crime Laboratory in Norfolk, conducted DNA analysis of the semen sample removed from the body of Ann Borghesani and the blood taken from Satcher. Guerrieri testified at trial that the DNA profiles obtained from the semen sample matched the DNA profiles of Satcher’s blood. Guerrieri testified further that each of the four probe tests matched the semen sample with the blood of Satcher, and that the four tests resulted in the overall elimination of 99.999998% of the black population.
Guerrieri also stated that “the probability of randomly selecting an unrelated individual from the black population with the DNA profile matching Mr. Satcher’s is approximately one in forty million.” In conclusion, Guerrieri estimated there are about fifteen million black males in the United States, and he expressed the opinion that the tests he performed would eliminate all but Satcher as the person who donated the semen removed from the body of Ann Borghesani.9
Satcher’s contentions raise the question whether DNA testing is a reliable scientific technique. However, as we indicated supra, that question has already been settled in Virginia. It was first settled in a series of cases decided by this Court, all involving one [241] Timothy Wilson Spencer: Spencer v. Commonwealth, 238 Va. 275, 384 S.E.2d 775 (1989), cert. denied, 493 U.S. 1036 (1990) (Spencer I); Spencer v. Commonwealth, 238 Va. 295, 384 S.E.2d 785 (1989), cert. denied, 493 U.S. 1093 (1990) (Spencer II); Spencer v. Commonwealth, 238 Va. 563, 385 S.E.2d 850 (1989), cert. denied, 493 U.S. 1093 (1990) (Spencer III).