LANDAU, J.
Appellant seeks reversal of an order committing him to the Mental Health Division based on findings that he is a danger to himself and unable to provide for his basic personal needs. ORS 426.005(1)(d)(A), (B). He argues that the trial court erred in “denying [him] the opportunity to subpoena witnesses for the hearing.” We affirm.
The relevant facts are not in dispute. In April 2001, appellant was brought before the Multnomah County Circuit Court based on a notice of mental illness filed by his mother and sister. They reported that appellant has a history of mental disorders dating from adolescence, that he had been off of his medications for the previous five months, that he had lost 30 to 40 pounds during that time, that he was hallucinating and yelling obscenities at people who do not exist, and that his home was filthy and full of cat feces, moldy food, and dirty laundry.
At the civil commitment hearing, appellant was represented by counsel. The hearing itself literally began with an outburst:
“[APPELLANT]: These are the people [appellant’s mother and sister] that I never visit with, but where are my sons at? They’re the ones that I live with all my life and raised. Okay? Yeah.
“THE COURT: Yeah.
“ [APPELLANT]: (inaudible).
“THE COURT: Well, sir, if you’ll bear with me just for a minute, I’m Judge Lawrence.
“[APPELLANT]: These people I never see. These people, see they, these people, they’ve been gone while I was raising my family. They were busy, you know, telling everyone else what to do.”
The court eventually was able to call the case number and introduce appellant to his court-appointed counsel. The court then attempted to describe to appellant the nature of the proceedings. When the court attempted to advise appellant that he had the right to subpoena witnesses, the following exchange occurred:
[11]*11“THE COURT: And he [counsel] could use the subpoena power, that is to say the power and process of the courts to compel the production of any evidence or witnesses who could speak in your favor. But I don’t believe that’s an issue, [counsel], or is it?
“[COUNSEL]: A hard time, you were speaking softly, he was—
“THE COURT: Subpoena, the subpoena.
“[APPELLANT]: Oh, is that, would you repeat the (inaudible)?
“[COUNSEL]: (Inaudible) whether we have any subpoenas?
“THE COURT: [Counsel] could use the subpoena power to compel the production of any evidence or witnesses who could speak in your favor.
“ [APPELLANT]: Oh, okay. I’d like my sons, both of my sons in here because they’re the only ones that live — I don’t live with these people, I don’t even see them.
“THE COURT: [Appellant]?
“ [APPELLANT]: All they do is just try to say — ■
“THE COURT: [Appellant]?
“[APPELLANT]: Oh (inaudible).
“THE COURT: Let me be straight with you about that, sir.
“ [APPELLANT]: With these guys—
“THE COURT: [Appellant]? I’m not going to put just—
“[APPELLANT]: What’s going on with these people and—
“THE COURT: [Appellant]?
“[APPELLANT]: And I don’t know what her problem is, and what all this false evidence that I—
* * * *
“[EXAMINER]: (Inaudible) the judge has to try and answer you, okay, about your sons, so—
[12]*12“THE COURT: Your, your sons are not going to be brought into your presence.
“[APPELLANT]: Why, why? Because they’re my, they’re the only ones that I spend time with every day—
“THE COURT: Because—
“[APPELLANT]: They’re the only ones that are witnesses. I, these people aren’t witnesses. And she filed false evidence against me, illegal, it’s false evidence. My kitchen floor is dirty, she says.
“THE COURT: I’m not going to put those children through this.
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“[COUNSEL]: (Inaudible), only witnesses that he’s requested.
“THE COURT: Right.
“[APPELLANT]: I’m requesting and you’re denying my truthful witness.
“[COUNSEL]: They could testify by phone as he suggested earlier or anything else, but at this point we would object both on the Oregon, U.S. Constitutional (inaudible), proceeding without being able to subpoena the witnesses that he’s requested.
“THE COURT: Thank you, [counsel]. The Court is satisfied that, that there is substantial likelihood that the children’s evidence would not be helpful to [appellant] under these circumstances.”
(Emphasis added.)
The report of the precommitment investigation was entered into evidence. Among other things, the report detailed appellant’s history of mental illness and current diagnosis of bipolar disorder with psychotic symptoms, including paranoid delusions and hallucinations. The mental examiner attempted to ask appellant some questions, but was persistently interrupted by appellant’s unresponsive outbursts. When questioned about whether he had been eating, he responded with a complaint about poisoning caused by a doctor. Appellant reported that he ate several times a day and that his diet consisted of vegetables, rice, milk, and [13]*13bread. When asked about the fact that his family reported a weight loss of 30 to 40 pounds, he replied that his antidepressant medication made him “blow up” and that the medication, when combined with others he had been prescribed, almost killed him. He said that he “fell dead on the floor” and that his sons could attest to that fact. He decided to stop taking the antidepressant and then began to lose weight. He insisted that he was at his normal weight. He then complained that he currently suffered a broken neck and back and that the doctor only prescribed him “poison.”
Appellant’s sister testified about the condition of appellant’s house, that there were cat feces all over the carpeting, that there was laundry soap all over the floor, food all over the house, severe mold, and a bucket of urine in the bath tub. She said that appellant would not drink water from the house because it was poisoned and that all his food was poisoned, as well. She said that appellant had not been eating and that he had told her that he was cooking vegetables “for his fish to eat.” She said that appellant yells and screams at people from his window at home or on the street. She complained that he yells profanity and once spit on a passing car and “flipped them off,” which resulted in the occupants of the car chasing a niece who was with them at the time. She said that appellant remained safe so far only because members of his family had been able to protect him. Appellant interrupted every question and every answer with interjections about, among other things, his broken neck and back, about people “breaking into innocent people’s houses,” about the failure of his sisters to help him clean the house or give him money, and about their testimony having been paid for by the examiners.
The trial court found that appellant suffers from a mental disorder, based on the reports of the examiners and “certainly by his affect today.” The court continued:
“THE COURT: He is indeed agitated, uncontrollable, angry—
; [APPELLANT]: Agitated? Shit yeah!
THE COURT: (Inaudible).
[14]*14“[APPELLANT]: Oh, he wanted me to be calm, am I calm, when she, but you’re so petty.
“THE COURT: He is not eating, and he is, the Court is satisfied that, if released, [appellant] today would be unable to care for his basic needs, that he’d be unable to feed himself—
“[APPELLANT]: I’ve been caring for myself for over forty years, Your Honor. That’s filthy. Bring my children in here—
“THE COURT: He’d be unable to clothe himself properly. He’d be unable to actually access funds for, for food.
“[APPELLANT]: —testify, that they’re filthy action[s], all your filthy actions. That’s a lie. I got food in my pocket! Look at my wallet. I still got food in my—
“THE COURT: And that there’s clear and convincing evidence that, as a result of his mental disorder, he is a danger to himself, particularly since he is confronting strangers on the streets.
“[APPELLANT]: That’s a filthy lie. It’s, are you, you, anybody else going to testify or is she just going to—
‡ ‡ ‡
“THE COURT: For those reasons, the Court does find upon clear and convincing evidence that [appellant] suffers from a mental disorder and is dangerous to himself and is unable to provide for his basic personal needs and is not receiving the care necessary for his health or safety.
“[APPELLANT]: Are you just (inaudible) or are, are you pressing—
“THE COURT: The Court further finds—
“ [APPELLANT]: —judgment against a good citizen.
“THE COURT: That [appellant] is either unwilling, unable or unlikely—
“[APPELLANT]: And then you’re going to dibble me for months and have me kill, I mean—
“THE COURT: —to participate in treatment on a voluntary basis—
[15]*15“[APPELLANT]: Sicker than I am because of your filthy food.”
The hearing ended with appellant yelling that his sisters wanted to kill him.
On appeal, appellant does not challenge the trial court’s findings on the merits. Instead, he argues that the trial court erred by “denying [him] the opportunity to subpoena witnesses for the hearing.” He argues that “the failure of the trial court to allow the allegedly mentally ill person to subpoena witnesses on his own behalf violates the Due Process Clause of the Fourteenth Amendment of the United States Constitution.”
The state argues that the assignment fails because (1) it is not preserved; (2) even if otherwise preserved, it is not reviewable because of a lack of an offer of proof; (3) even if the assignment is reviewable, there was no error because appellant has failed to demonstrate that the trial court abused its discretion; and (4) even if there was error, it was harmless.
We begin with the issue of preservation and the scope of any assignment of error that is properly before us. The phrasing of the assignment itself is perplexing. It is couched in terms of the trial court’s erroneous denial of an “opportunity” to subpoena witnesses. Appellant, however, never explains precisely how the trial court denied him an “opportunity” to subpoena witnesses.
Under ORCP 55 C(1)(a)(ii), a subpoena to require attendance before a court “may be issued by an attorney of record of the party to the action in whose behalf the witness is required to appear, subscribed by the signature of such attorney” without the trial court having to do anything. Indeed, that is precisely what the trial court repeatedly told appellant, that is, that “he [appellant’s counsel] could use the subpoena power” to compel the production of witnesses to appear in court “who could speak in your favor.” When appellant complained that he wanted his children to testify, the trial court advised him that it would not permit them to testify, that it was satisfied that their testimony “would not be helpful to [appellant] under these circumstances.” In response, appellant’s counsel’s only objection was “on the Oregon, U.S. [16]*16Constitution (inaudible) proceeding without being able to subpoena the witnesses that he’s requested.”
Thus, at least as we understand the record, the focus of the assignment of error is not that the trial court failed to issue a subpoena; under the rules, counsel could have issued a subpoena without the trial court’s involvement. Nor is appellant’s complaint that the trial court somehow interfered with appellant’s counsel’s authority to issue a subpoena on his own, as allowed by rule; to the contrary, the court repeatedly advised appellant of his counsel’s authority to issue subpoenas on his own.
The focus of appellant’s assignment instead is either that (1) the trial court unconstitutionally “proceed [ed] ” without first giving appellant’s counsel the time to subpoena witnesses, that is, the trial court failed to allow appellant a continuance; or (2) the trial court erred in sua sponte declaring that, even if counsel were to subpoena the children, the court would exclude their testimony.
The problem is that appellant never asked the trial court for a continuance. See ORS 426.095(2)(c) (court may, for good cause shown, postpone hearing for up to five judicial days). Thus, the only issue that arguably is preserved is whether the trial court erred in declaring that, even if subpoenaed, the children would not be permitted to testify.1
Even assuming that that issue otherwise has been preserved, however, it is not reviewable because of the absence of an offer of proof. As a general rule, a party objecting to the exclusion of evidence must supply an offer of proof. State v. Affeld, 307 Or 125, 128, 764 P2d 220 (1988). As the Supreme Court has explained, there are two main purposes of an offer of proof:
“One purpose of an offer of proof is to assure that appellate courts are able to determine whether the ruling was erroneous. * * * Another purpose of an offer of proof is to assure that the trial court can make an informed decision. An offer [17]*17of proof permits the parties to raise additional arguments, if appropriate, and gives the court an opportunity to reconsider its ruling and correct any error.”
State v. Olmstead, 310 Or 455, 461, 800 P2d 277 (1990) (citations omitted). An offer of proof can be made by question and answer or by counsel summarizing what the proposed evidence is expected to be. State v. Phillips, 314 Or 460, 466, 840 P2d 666 (1992). Either method is adequate “if we are able to determine whether it was reversible error to exclude proffered evidence.” State v. Wonderling, 104 Or App 204, 207, 799 P2d 1135 (1990).
In this case, appellant failed to make any offer of proof. His counsel did object and propose that the children be allowed to testify by telephone, but he offered no suggestion as to the content of the expected testimony. Without any record of what the children would have said if called to testify, we cannot evaluate whether the trial court erred in excluding the testimony.
We turn to the dissenting opinions. Judge Edmonds begins by characterizing the scope of the assignment as whether the trial court erred in “refusing” to permit appellant to exercise his statutory right to subpoena witnesses. Having so broadly characterized the assignment, he finds it easy to conclude that the trial court erred, because the right to subpoena witnesses is statutorily — indeed, constitutionally — guaranteed. According to Judge Edmonds, no offer of proof is necessary to determine that the trial court committed reversible error, because the trial court’s ruling was “procedural in nature and not dependent on the particular substantive evidence that could flow therefrom had the ruling! ] not been made.” 192 Or App at 28 (Edmonds, J., dissenting).
The short answer to Judge Edmonds is that he is attacking a straw person. As we have noted, the trial court did not refuse to permit counsel to subpoena any witnesses. The court ruled instead that, if subpoenaed, the children would not be permitted to testify because “there is substantial likelihood that the children’s evidence would not be helpful” to appellant. Thus, the court made an evidentiary ruling to exclude testimony based on its substantive content.2 Even [18]*18Judge Edmonds acknowledges that, in such cases, an offer of proof is required. See 192 Or App at 27 (Edmonds, J., dissenting) (“ ‘Normally, an offer of proof is required to preserve error when a trial court excludes testimony.’ ” (quoting Affeld, 307 Or at 128)). Indeed, Judge Edmonds’s own opinion at one point acknowledges that the trial court “ultimately justified its refusal to permit [appellant] to subpoena his sons as witnesses on substantive grounds.” 192 Or App at 24 (Edmonds, J., dissenting). If the court’s ruling excluding the children’s testimony was based on “substantive grounds,” then it necessarily follows that we must know the substance of the testimony to evaluate the correctness of the ruling.
Even assuming for the sake of argument that Judge Edmonds is correct that the trial court’s ruling was more in the nature of a procedural ruling that, in effect, deprived appellant of the ability to subpoena witnesses, a harmless error analysis still is required. Directly on point in that regard is State v. Bartel-Dawson, 176 Or App 519, 520, 31 P3d 1129 (2001). In that case, the trial court failed to advise the appellant at a mental commitment hearing of her right to subpoena witnesses. The state conceded error but argued [19]*19that the error was harmless. We agreed with the state that “a harmless error analysis applies” to such cases. Id. at 520 (citing State v. Cach, 172 Or App 745, 750 n 4, 19 P3d 992, rev den, 332 Or 316 (2001) (Kistler, J., majority) and 172 Or App at 754 (Edmonds, P. J., concurring). Thus, the trial court’s supposed refusal to permit counsel to subpoena witnesses is not, by itself, the equivalent of “structural error” that requires no harmless error analysis. And, in the absence of a record as to the nature of the testimony that was thereby excluded, we cannot determine in this case whether the trial court’s supposed error in fact was harmless.
We turn to Judge Armstrong’s dissent. He acknowledges the evidentiary nature of the trial court’s ruling and, in consequence, the need for an offer of proof. He nevertheless argues that we are in a position to determine that the trial court committed reversible error in excluding the testimony of appellant’s children because, although counsel did not make an offer of proof as such, there is adequate information that may be culled from the various statements of appellant throughout the hearing for us to determine what the children would have said. According to Judge Armstrong, it is clear that the children would have given testimony about appellant’s weight loss, about his ability to care for his basic needs, and that the exclusion of that testimony was not harmless.
At the outset, we respectfully disagree with Judge Armstrong that this court is obligated to comb through a record in an attempt to reconstruct, from appellant’s many outbursts, suggestions as to what the children might have said if called to testify. As we have noted, the relevant case law requires that counsel either make a representation to the court summarizing the expected testimony or put a witness on the stand and make a formal offer of proof. E.g., Phillips, 314 Or at 466. In this case, counsel did neither.
Even assuming for the sake of argument that, in the abstract, Judge Armstrong is correct that it is appropriate for us to attempt to piece together portions of a record to satisfy the offer of proof requirement, the fact remains that, in this case, the fragments that appellant offers are not sufficient to enable us to determine whether the trial court committed reversible error. At best, appellant informed the court that [20]*20(1) he had more than one child, (2) they lived with him for some undisclosed amount of time, (3) he wanted them to testify, and (4) they could testify that he “fell dead on the floor” because of a problem with his antidepressant medications. It could be argued — as Judge Armstrong certainly does — that appellant also expected his children to testify about his ability to care for himself and his weight loss. But, even assuming that so much could be inferred from appellant’s remarks, the content of that testimony remains a matter of speculation. Would the children have testified about the cat feces on the carpet? The laundry soap on the floor? The food all over the house? The severe mold? The urine in the bucket? What exactly would the children have said about those facts? That there were no cat feces on the carpet? Only some cat feces on the carpet? That there was no mold all over the house? That any mold in the house was not severe? There is simply no way to tell from the state of the record any of the answers to such questions.
Finally, even assuming for the sake of argument that Judge Armstrong is correct, we nevertheless would conclude that any error was harmless. Judge Armstrong asserts that the children reasonably could be expected to have testified favorably about appellant’s ability to care for his basic needs and about his weight loss. Assuming that to be the case, the record remains uncontradicted that appellant has a history of mental illness dating from adolescence, that he suffers from bipolar disorder accompanied by paranoid delusions and hallucinations, that he irrationally fears that people are trying to poison him, that he has refused to take his antidepressant medications, that he dropped 30 to 40 pounds — whether because of a failure to eat (as his sister testified) or because he stopped taking his medication (as appellant testified) — in a short period of time, and that he yells and makes obscene gestures at complete strangers — including passing cars — resulting on at least one occasion in family members being threatened. Moreover, his bizarre behavior at the time of the hearing, which lends credence to the suggestion of the examiners and appellant’s family that he is dangerous and cannot care for himself, cannot be ignored.
In short, we conclude that appellant’s assignment of error is not reviewable and that, even if it were, any error [21]*21that the trial court committed in excluding the testimony of the children was harmless.
Affirmed.