This case presents, as a matter of first impression, 1 constitutional challenges to G. L. c. 231, § 60B, which establishes a procedure for the screening, by a tribunal, of all actions for “malpractice, error or mistake against a provider of health care.” See St. 1975, c. 362, § 5. The plaintiffs’ medical malpractice action was dismissed when they failed to satisfy a $2,000 bond requirement imposed on them, after a tribunal hearing, as a condition for the continuance of their action. They have appealed the dismissal, contending that the tribunal procedure violates equal protection, due process, and separation of powers *647 provisions of the Massachusetts and United States Constitutions. We granted an application for direct appellate review. G. L. c. 211A, § 10 (A).
Robert Paro brought this action in his own right and as next friend for his daughter Lynn Marie. Lynn Marie was born on the premises of the defendant Longwood Hospital (hospital), and employees of the hospital aided in her delivery. The plaintiffs assert that, following the birth, these employees negligently applied silver nitrate to Lynn Marie’s eyes, 2 and negligently failed to administer proper care to correct their mistake after the improper application. They contend that this negligence resulted in a scar on Lynn Marie’s left cheek which remains visible to this day. 3
Following the filing of the complaint and answer, both parties appeared before a malpractice tribunal constituted pursuant to G. L. c. 231, § 60B, the recently enacted medical malpractice tribunal procedure. The plaintiffs made an offer of proof and the hospital report and some photographs of Lynn Marie were entered in evidence. The panel decided for the defendant, holding “that the evidence submitted by the plaintiff, even if properly substantiated, [was] not sufficient to raise a legitimate question of liability appropriate for judicial inquiry.” A bond of $2,000 was imposed on the plaintiffs as a condition for continuance of the action. A motion for reduction of the bond amount, on grounds of financial hardship, was denied. When the plaintiffs did not file the bond within the allotted period, the action was dismissed.
General Laws c. 231, § 60B, was enacted in 1975 as part of a comprehensive package designed to ensure the continued availability of medical malpractice insurance at a reasonable cost. St. 1975, c. 362. Section 60B requires that all actions alleging medical malpractice be presented, within fifteen days of the filing of the defendant’s answer,
*648
to a tribunal consisting of a Superior Court judge, an attorney, and a representative of the health care industry,
4
the latter two appointed by the judge. The tribunal is charged with determining, on the basis of an offer of proof made by the plaintiff, whether “a legitimate question of liability appropriate for judicial inquiry” is presented. If the panel decides that such a question does not exist in a plaintiff’s case, and thus finds for the defendant, the judge-member is required to impose a bond on the plaintiff as a condition for further prosecution. The bond is payable to the defendant for his costs if he ultimately prevails. The statute specifies that the bond amount be set at $2,000, but provides discretion to the judge to increase the amount or, if he finds that the plaintiff is indigent, to decrease it. If the plaintiff does not file the required bond within thirty days, the action must be dismissed.
Austin
v.
Boston Univ. Hosp.,
The Paros attack the statutory procedure by alleging that it is in violation of the Constitutions of both Massachusetts and the United States on equal protection, due process, and separation of powers grounds. We deal with each claim to the extent that it is properly raised in this case, and find no constitutional impediment.
1. Equal protection of the laws. The plaintiffs contend that two classifications made by the tribunal statute — medical malpractice victims versus victims of other torts, and plaintiffs versus defendants 5 — violate their rights to equal protection of the law as guaranteed by the Four *649 teenth Amendment to the Constitution of the United States and comparable provisions of the Massachusetts Constitution. We disagree.
Classification is an integral part of the legislative task and will not be interfered with by a judicial body unless the distinctions drawn by the enactment are “arbitrary or irrational,” or result in “invidious” discrimination.
Pinnick
v.
Cleary,
A party challenging the constitutionality of a legislative enactment bears the burden of proving that the proper standard of review is not satisfied.
Zayre Corp., supra
at 433.
Consolidated Cigar Corp.
v.
Department of Pub.
*650
Health,
No claim is made in this case that a fundamental interest or suspect class .is involved, and it is therefore conceded that the applicable test is the rational basis standard. 7 Additionally, the plaintiffs admit that the purpose that the statute is intended to serve, assuring the continued availability of medical malpractice insurance, see St. 1975, c. 362, is a proper object of legislation. The plaintiffs argue, however, that the two classifications that they challenge do not actually promote this goal.
The record of the proceedings below does not indicate that any findings of fact were made or requested on the question whether the tribunal procedure was rationally related to its stated purpose. An evidentiary hearing and findings of fact may be appropriate in a constitutional challenge to a statute,
Henry’s Drywall Co., supra
at 541 n.4; factual assertions in an appellate brief are not a - substitute. See
Bannish
v.
Bahnish,
2. Due process. The plaintiffs raise both procedural and substantive due process challenges to the tribunal procedure, and allege that it is in violation of the jury trial (art. 15) and purchase of justice (art. 11) clauses of the Massachusetts Declaration of Rights. They argue principally that the bond requirement cuts off their access to *652 the courts, thus denying them their constitutional right to be heard. 9
In limited circumstances statutes that have imposed financial obstacles to the obtaining of access to the courts have been struck down on due process grounds. Most of these cases have involved challenges by criminal defendants, for whom a judicial hearing is a matter of substantial importance. See, e.g.,
Douglas
v.
California,
We need not and do not decide whether a financial obstruction to the institution of a medical malpractice suit would fall into this limited category. The constitutional issue is avoided in this case because of the wide discretion that the statute gives to the judge to set the bond amount. As long as the discretion is ^exercised without unreason *653 ably prohibiting meritorious claims, no constitutional violation will exist.
The issue here falls within the principles set forth in
Damaskos
v.
Board of Appeal of Boston,
The medical malpractice tribunal procedure satisfies the standard set by the Damaskos court. No bond is required for claims that the tribunal determines have some legal merit. This alone might be sufficient to satisfy the Damas-kos standard, since it can be reasonably argued that any claim that does not satisfy the tribunal is of questionable merit, and thus is not entitled to the protection requested. We need not go so far, however, since the statute provides the judge with discretion in setting the bond amount for those cases that the panel finds have no legal merit. The judge is authorized by the statute (G. L. c. 231, § 60B) to set the bond at $2,000 or higher. He is also authorized to fix an amount below $2,000 where he finds that the plaintiff is indigent, 10 but he may not eliminate the requirement of a bond. The $2,000 level is not unreasonably *654 burdensome for nonindigent plaintiffs whose claims have already been the subject of adverse findings by the statutory tribunals. Thus the procedure conforms to the Da-maskos holding and does not violate constitutional principles.
The plaintiffs next contend that their rights under art. 11 of the Massachusetts Declaration of Rights “to obtain right and justice freely, and without being obliged to purchase it,” have been violated. The object of this provision is to guarantee the availability of equal justice, “that all litigants similarly situated may appeal to the courts both for relief and for defence under like conditions and with like protection and without discrimination.”
Old Colony R.R.
v.
Assessors of Boston,
The plaintiffs also argue that the bond requirement violates their right to a jury trial because it obstructs their access to a jury. Art. 15, Massachusetts Declaration of Rights. The right to a jury trial is not absolute; it “may be regulated as to the mode in which the right shall be exercised so long as such regulation does not impair the substance of the right.”
Orasz
v.
Colonial Tavern, Inc.,
The plaintiffs finally assert that the tribunal procedure is unconstitutional because it abrogates their common law rights without providing a reasonable alternative. This is essentially a substantive due process argument.
This court has never been squarely presented with the issue of whether the Legislature can abrogate a common law right without providing a substitute.
Pinnick
v.
Cleary,
3.
Separation of powers.
The plaintiffs contend that § 60B violates art. 30 of the Declaration of Rights of the Massachusetts Constitution.
11
They claim that the mal
*656
practice panel falls within the legislative branch of the government, and that it interferes with the judiciary because its findings are admissible at trial, because it obstructs access to a judicial hearing, and because its two nonjudicial members can override decisions of the judge. We do not address the first claim because, since the plaintiffs did not go to trial and did not have the finding admitted against them, they have no standing to raise the issue.
Massachusetts Comm’n Against Discrimination
v.
Colangelo,
Article 30 requires that each of the legislative, executive, and judicial departments maintain its independence from the others, and that it shall not exercise any powers of the other two departments. However, the exact lines between what constitutes legislative, executive, and judicial powers have never been precisely drawn.
Commonwealth
v.
Jackson,
The contention that the malpractice tribunal is a legislative body which obstructs entrance to the judicial system fails on two grounds. First, as we have previously discussed,
12
the tribunal procedure does not act as an
*657
obstruction because the judge has discretion to set the bond amount at a level that will not unduly burden meritorious suits. Additionally, the tribunal procedure, in its role as a first step in obtaining judicial access, does not function as a part of the legislative department, but as a part of the judicial department. The role of the tribunal in hearing the plaintiff’s offer of proof, receiving evidence, and determining the legal sufficiency of the claim, is a part of the judicial process at the preliminary stages of an action seeking damages for alleged medical malpractice. See
LaChapelle, supra
at 168-170. The tribunal’s intimate connection with the judicial proceeding makes it clear that the hearing procedure is itself a part of the judicial process. There is no violation of art. 30. See
LaChapelle, supra
at 170;
Boston, petitioner,
Finally, the plaintiffs argue that § 60B is unconstitutional because it allows the two lay panel members to override the judge in the decision of purely legal issues, such as questions relating to the admissibility of evidence. See
Wright
v.
Central Du Page Hosp. Ass’n,
4. None of the constitutional challenges to the medical malpractice tribunal procedure, G. L. c. 231, § 60B, that *658 were raised have been sustained. The action was therefore properly dismissed.
Judgment affirmed.
Notes
In
Austin
v.
Boston Univ. Hosp.,
According to the plaintiff’s brief, silver nitrate is routinely applied to the eyes of a newborn child to prevent infection.
At the commencement of the action, Lynn Marie was ten years old.
If the defendant is a physician, the health care member must also be a physician. If the defendant is any other health care provider, the third member must be “a representative of that field of medicine in which the alleged tort or breach of contract occurred.” G. L. c. 231, § 60B.
The plaintiffs also argue that a third classification made by the statute violates equal protection guaranties — medical malpractice tortfeasors versus all other tortfeasors. Even if a basis for challenge existed here, the plaintiffs would have no standing to raise it since they belong to neither class of tortfeasors.
Massachusetts Comm’n Against Discrimination
v.
Colangelo,
The plaintiffs contend that a third equal protection standard, falling between the “rational basis” and “strict scrutiny” tests, has been recognized by the Supreme Court of the United States. The existence of this so called “strict rationality” test has been a matter of recent controversy. See, e.g.,
Massachusetts Bd. of Retirement
v.
Murgia,
The plaintiffs make this concession although they argue the existence of a third tier of equal protection analysis. See note 6 infra.
For a discussion of the effectiveness of the Massachusetts procedure in screening doubtful claims, see McLaughlin, A Look at the Massachusetts Malpractice Tribunal System, 3 Am. J. L. & Med. 197, 201-202 (1977).
The plaintiffs also argue that the statute violates their right to procedural due process in other ways. They claim that the absence of a provision in the statute for challenging the composition of the panel, in case of some partiality of a member, made the procedure unfair. They also contend that the requirement that the hearing be held within fifteen days of the filing of the defendant’s answer did not give them a sufficient opportunity for discovery. However, neither of these assertions was raised below by an appropriate motion; they are thus not properly before us now.
Royal Indem. Co.
v. Blakely,
The plaintiffs also argue, with some support from other jurisdictions, see, e.g.,
Simon
v.
St. Elizabeth Medical Center,
Indigency is not defined in this section. General Laws c. 261, § 27A, inserted by St. 1974, c. 694, § 3, relating to the payment of court costs by indigent litigants, defines an indigent as “a person who is unable to pay the fees and costs of the proceeding in which he is involved, or is unable to do so without depriving himself or his dependents of *654 the necessities of life, including food, shelter and clothing.” This definition provides a judge with sufficient guidance and discretion to accomplish the goals outlined here.
Article 30 provides: “In the government of this commonwealth, the legislative department shall never exercise the executive and judicial powers, or either of them: the executive shall never exercise the legislative and judicial powers, or either of them: the judicial shall never exercise the legislative and executive powers, or either of them: to the end it may be a government of laws and not of men.”
See infra at 652-654.
