concurring in part.
I join the opinion of the Court except for Part IV-B. I agree with Part IV-B insofar as the Court holds that qualified and independent assistance must be provided to an inmate who is threatened with involuntary transfer to a state mental hospital. I do not agree, however, that the requirement of independent assistance demands that a licensed attorney be provided.1
*498I
In Gagnon v. Scarpelli, 411 U. S. 778 (1973), my opinion for the Court held that counsel is not necessarily required at a probation revocation hearing. In reaching this decision the Court recognized both the effects of providing counsel to each probationer and the likely benefits to be derived from the assistance of counsel. “The introduction of counsel into a revocation proceeding [would] alter significantly the nature of the proceeding,” id., at 787, because the hearing would inevitably become more adversary. We noted that probationers would not always need counsel because in most hearings the essential facts are undisputed. In lieu of a per se rule we held that the necessity of providing counsel should be determined on a case-by-case basis. In particular, we stressed that factors governing the decision to provide counsel include (i) the existence of factual disputes or issues which are “complex or otherwise difficult to develop or present,” and (ii) “whether the probationer appears to be capable of speaking effectively for himself.” Id., at 790, 791.
Consideration of these factors, and particularly the capability of the inmate, persuades me that the Court is correct that independent assistance must be provided to an inmate before he may be transferred involuntarily to a mental hospital. The essence of the issue in an involuntary commitment proceeding will be the mental health of the inmate. The resolution of factual disputes will be less important than the ability to understand and analyze expert psychiatric testimony that is often expressed in language relatively incomprehensible to laymen. It is unlikely that an inmate threatened with involuntary transfer to mental hospitals will possess the competence or training to protect adequately his own interest in these state-initiated proceedings. And the circumstances of being imprisoned without normal access to others who may assist him places an additional handicap upon an inmate’s ability to represent himself. I therefore agree *499that due process requires the provision of assistance to an inmate threatened with involuntary transfer to a mental hospital.
II
I do not believe, however, that an inmate must always be supplied with a licensed attorney. “[D]ue Process is flexible and calls for such procedural protections as the particular situation demands.” Morrissey v. Brewer, 408 U. S. 471, 481 (1972). See Mathews v. Eldridge, 424 U. S. 319, 334-335 (1976). Our decisions defining the necessary qualifications for an impartial decisionmaker demonstrate that the requirements of due process turn on the nature of the determination which must be made. “Due Process has never been thought to require that the neutral and detached trier of fact be law trained or a judicial or administrative officer.” Parham v. J. R., 442 U. S. 584, 607 (1979). In that case, we held that due process is satisfied when a staff physician determines whether a child may be voluntarily committed to a state mental institution by his parents. That holding was based upon recognition that the issues of civil commitment “are essentially medical in nature,” and that “ ‘neither judges nor administrative hearing officers are better qualified than psychiatrists to render psychiatric judgments.’ ” Id., at 607, 609, quoting In re Roger S., 19 Cal. 3d 921, 942, 569 P. 2d 1286, 1299 (1977) (Clark, J., dissenting). See also Morrissey v. Brewer, supra, at 489; Goldberg v. Kelly, 397 U. S. 254, 271 (1970).
In my view, the principle that due process does not always require a law-trained decisionmaker supports the ancillary conclusion that due process may be satisfied by the provision of a qualified and independent adviser who is not a lawyer. As in Parham v. J. R., the issue here is essentially medical. Under state law, a prisoner may be transferred only if he “suffers from a mental disease or defect” and “cannot be given proper treatment” in the prison complex. Neb. Rev. *500Stat. § 83-180 (1) (1976), The opinion of the Court allows a nonlawyer to act as the impartial decisionmaker in the transfer proceeding. Ante, at 496.2
The essence of procedural due process is a fair hearing. I do not think that the fairness of an informal hearing designed to determine a medical issue requires participation by lawyers. Due process merely requires that, the State provide an inmate with qualified and independent assistance. Such assistance may be provided by a licensed psychiatrist or other, mental health professional. Indeed, in view of the nature of the issue involved in the transfer hearing, a person possessing such professional qualifications normally would be preferred. As the Court notes, “[t]he question whether an individual is mentally ill and cannot be treated in prison ‘turns on the meaning of the facts which must be interpreted by expert psychiatrists and psychologists.’ ” Ante, at 495, quoting Addington v. Texas, 441 U. S. 418, 429 (1979). I would not exclude, however, the possibility that the required assistance may be rendered by competent laymen in some cases. The essential requirements are that the person provided by the State be competent and independent; and that he be free to act solely in the inmate’s best interest.
In sum, although the State is free to appoint a licensed attorney to represent an inmate, it is not constitutionally required to do so. Due process will be satisfied so long as an inmate facing involuntary transfer to a mental hospital is provided qualified and independent assistance.
Mr. Justice Stewart,with whom The Chief Justice and Mr. Justice Rehnquist join, dissenting.
It seems clear to me that this case is now moot. Accordingly, I would vacate the judgment and remand the case to *501the District Court with directions to dismiss the complaint. United States v. Munsingwear, Inc., 340 U. S. 36.
As the Court points out, this is not a class action, and the appellee is now incarcerated in the Nebraska Penal and Correctional Complex with an anticipated release date in March 1982. See ante, at 485-487, and n. 3. In that status, the appellee is simply one of thousands of Nebraska prisoners, with no more standing than any other to attack the constitutionality of Neb. Rev. Stat. § 83-180 (1) (1976) on the sole basis of the mere possibility that someday that statute might be invoked to transfer him to another institution.
Although the appellee was once transferred in accord with § 83-180 (1), there is no demonstrated probability that that will ever happen again. Weinstein v. Bradford, 423 U. S. 147. And this case is not one that by its nature falls within the ambit of the “capable of repetition, yet evading review” exception to established principles of mootness. See Southern Pacific Terminal Co. v. ICC, 219 U. S. 498; Super Tire Engineering Co. v. McCorkle, 416 U. S. 115. If the appellee should again be threatened with transfer under the allegedly infirm statute, there will be ample time to reach the merits of his claim.
“ ‘To adjudicate a cause which no longer exists is a proceeding which this Court uniformly has declined to entertain.’ Brownlow v. Schwartz, 261 U. S. 216, 217-218.” Oil Workers v. Missouri, 316 U. S. 363, 371.
I also agree with the Court’s holding that this case is not moot. The question is whether appellee faces a substantial threat that he will again be transferred to a state mental hospital. See Doran v. Salem, Inn, Inc., 422 U. S. 922, 930-932 (1975); Steffel v. Thompson, 415 U. S. 452, 458-460 (1974); Doe v. Bolton, 410 U. S. 179, 188 (1973). He was involuntarily transferred from the prison complex to a mental institution, and thereafter paroled upon condition that he continue to receive psychiatric treatment. When he violated parole, he was returned to prison. The State advises us that appellee’s “history of mental illness indicates a serious threat to his own safety, as well as to that of others,” and “there is a very real expectation” of transfer if the District Court injunction were removed. App. to Juris. Statement 24. The District Court concluded that appellee is under threat of transfer. In these circumstances it is clear that a live controversy remains in which appellee has a personal stake. See Seatrain Shipbuilding Corp. v. Shell Oil Co., 444 U. S. 572, 581-583 (1980).
The District Court specifically held that “a judicial officer is not required, and the decisionmaker need not be from outside the prison or hospital administration.” Miller v. Vitek, 437 F. Supp. 569, 574 (Neb. 1977) (three-judge court).