dissenting:
The majority concludes that in each of the four challenged discovery rulings the district court abused its discretion in denying J.P.’s (plaintiff) motions for supplemental disclosure of witnesses and permitting further discovery. In my opinion, the district court’s rulings were not an abuse of discretion but rather, constituted a reasonable attempt at docket control and case management which is permissible under C.R.C.P. 16. Therefore, I dissent.
I
Plaintiffs first discovery request sought the endorsement of Dr. Day as a substitute for three previously endorsed experts in the area of orthopedic surgery. Plaintiff explained that problems had arisen with respect to each of her other three experts and thus, the endorsement of Dr. Day was needed. The majority concludes that the denial of this motion constituted an abuse of discretion because “[ojrthopedic issues are relevant to the underlying action” and “the defendants would not suffer prejudice if Dr. Day were endorsed.” Maj. op. at 753.
The second request sought to endorse an economist, Dr. Pacey, in plaintiffs expert designation whose name and summary of opinions had initially been omitted from that designation. The majority disregards the trial court’s conclusion that the summary of Dr. Pacey’s opinions were not provided in a timely manner and instead, holds that “any potential prejudice [to defendants] is cured by the continuance of the trial.” Maj. op. at 754.
The third discovery request sought the endorsement of two law enforcement officials (Booth and Adams) who had investigated the murder of the donor whose tissue was used in plaintiffs operation. Plaintiff argued Booth and Adams’ testimony would bear on the question of the appropriateness of using the donor’s tissue. While acknowledging that the endorsement of these witnesses could have been submitted earlier, the majority holds that the failure to timely endorse these witnesses “was neither willful, grossly negligent, prejudicial, nor made in bad faith.” Maj. op. at 755-756. Thus, the majority concludes the trial court abused its discretion in denying this request.
Finally, after the trial court permitted plaintiff to endorse two new witnesses (Grooms and Teachy) who had information bearing on LifeNet’s donor screening practices, plaintiff moved to endorse additional witnesses discovered as a result of the information provided by Grooms and Teachy. The trial court refused to allow the additional discovery. Again, the majority concludes that this additional discovery should have been permitted because the significance of the other witnesses was not previously *758known to plaintiff and “defendants would not be prejudiced by the introduction of new and relevant evidence-” Maj. op. at 757.1
In short, the majority holds that in each instance, because the sought after discovery will be helpful to plaintiff’s case and because defendants will not be prejudiced by undue surprise as a result of the two continuances of the original trial date, the trial court abused its discretion in denying plaintiffs motions.2 In my opinion, by emphasizing plaintiffs need and the remedial effects of the trial continuances, the majority has significantly intruded upon the ability of trial courts to exercise their discretion in guiding pretrial discovery, managing complex civil cases, and controlling their dockets.
II
The purposes of Rule 16 include not only providing adequate time for parties to prepare for trial and the avoidance of undue surprise and trial by ambush but also, “[t]he purpose of this Rule 16 is to define and clarify the responsibilities of and options available to the parties and the court to facilitate a fair and speedy resolution of civil disputes with a minimum of inconvenience and expense.” C.R.C.P. 16. “A trial data certificate serves an important function in aiding docket control, standardizing local pre-trial procedure, and requiring the parties to focus their issues.” Nagy v. District Court, 762 P.2d 158, 162 (Colo.1988).
While Rule 16 does not address the effect of a trial continuance on disclosure deadlines, the rule clearly requires early disclosure. Detailed disclosure is required within 180 days after the case is at issue. C.R.C.P. 16(a). In this initial disclosure, each party is required to disclose claims and defenses, undisputed and disputed issues, legal authorities, damage claims, proposed stipulations, factual and expert witnesses, exhibits, settlement information, and a discovery plan specifying the type of discovery, time frames and from whom discovery will be sought. C.R.C.P. 16(a)(I)-(XV).
Supplementation of the disclosure certificate is not a matter of unrestricted right but is subject to the procedures and standards set forth in C.R.C.P. 16(b). Certain matters may be supplemented at any time, such as stipulations and undisputed facts. See C.R.C.P. 16(b)(5). Other matters, such as statement of claims and defenses, disputed issues, points of law and itemization of damages, may be supplemented “if not known at the time of the filing of the disclosure certificate.” C.R.C.P. 16(b)(1). Supplementation of lay witnesses is permitted if their identity and or significance was not known at the time of the filing of the disclosure certificate. “The supplementation shall state why the witness could not have been disclosed earlier.” C.R.C.P. 16(b)(2). Supplementation of expert witnesses is allowed if “not known at the time of the filing of the disclosure certificate. ... The supplementation shall set forth the subject matter of the expert’s testimony and state why the expert could not have been disclosed earlier.” C.R.C.P. 16(b)(4). These requirements plainly are intended to avoid a never-ending chain of supplemental endorsements by prescribing a time frame in which such endorsements are required, and allowing the extension of that *759time period when necessary, to prevent manifest injustice. See C.R.C.P. 16(c).
Whether to allow for additional endorsements of witnesses is a determination committed to the discretion of the trial court and its ruling will be disturbed only on a showing that it was manifestly arbitrary, unfair, or unreasonable. Cherry Creek School Dist. No. 5 v. Voelker, 859 P.2d 805, 810 (Colo.1993); People v. Milton, 732 P.2d 1199, 1207 (Colo.1987). When the requirements of C.R.C.P. 16 are applied to the discovery motions at issue here, it is clear that the trial court did not abuse its discretion in denying those motions.
Ill
The significance of issues pertaining to orthopedic surgery has been known to all the parties since the case began. In my judgment, plaintiff has failed to meet the requirement of showing why she could not endorse a suitable expert in this area in her initial disclosure certificate. It was alleged that plaintiffs problems with her experts were the result, in part, of interference and pressure exerted by some of the defendants. However it was also alleged that plaintiff was merely seeking to secure a better expert than the one she initially commissioned. The trial court was in the best position to assess what plaintiff was trying to achieve by endorsing Dr. Day and why.3 Such a determination is, of course, the type which is left to the discretion of the trial court. This judgment should not be second guessed absent an abuse of discretion.
So too with economic issues Dr. Pacey is expected to testify to. As the trial court’s order denying the endorsement of Dr. Pacey states: “At no time has a proposed endorsement of Dr. Pacey been filed with the court which is in compliance with C.R.C.P. 16_” Though the trial court was willing to accept plaintiffs explanation that “the word processor [was responsible for] deleting Dr. Pacey’s proper endorsement,” this fact alone does not mandate that a court permit the supplemental endorsement of witnesses — bad faith is not required in order to deny supplemental endorsements. See infra pp. 760-761. Moreover, for the reasons identified by the trial court, no manifest injustice will result to plaintiff if Dr. Pacey is not permitted to testify because “[n]o defendant has endorsed an economist to testify as an expert witness” and in light of the fact that “juries commonly decide the amount of damages without the assistance from an expert witness.”
Similarly, plaintiff knew of Booth and Adams in December of 1992 when their affidavits were obtained. For reasons that are not immediately apparent however, plaintiff failed to endorse these potential witnesses in the disclosure certificate on February 9, 1993. While the majority may be correct in noting that their testimony will be useful in plaintiffs case and that defendants may not be prejudiced in light of the trial continuance, the fact remains that plaintiff has failed to explain why these witnesses could not have been endorsed earlier as required by C.R.C.P. 16(b)(4).4
The trial court allowed the endorsement of Grooms and Teachy. However, the court also cut off further discovery resulting from these witnesses. In light of the purposes of Rule 16, it was not an abuse of discretion for the trial court to close off further discovery. *760Plaintiff has sought to endorse four additional -witnesses as a result of interviews with Grooms and Teachy. What additional information will emerge from interviewing the four additional witnesses? And what further information might be gained from that information? At some point, discovery must end and the case must go to trial.
In my opinion, the trial court’s denial of each of the discovery requests was reasonable and consistent with the mandates of Rule 16. Each ruling is warranted on the grounds that plaintiff had failed to comply with the express provisions of Rule 16 or constituted a reasonable means of effectuating the policies underlying Rule 16. I am willing to concede that, based on an analysis such as that proposed by the majority, it would have been reasonable for the trial court to grant each of the motions. However reaching a contrary conclusion, as the trial court did, falls far short of an abuse of discretion.
IV
In the name of liberally construing pretrial discovery rules, the majority has ignored the express requirements of Rule 16. The majority makes no attempt to show that Dr. Pacey, Booth or Adams could not have been properly endorsed earlier. Rather, the majority concludes that because plaintiff has not acted in bad faith, the sought after information will be useful to her case, and because defendants will suffer no prejudice in light of the trial continuances, the trial court should have reopened discovery in this case. Such a conclusion not only is contrary to the purposes of Rule 16, it ignores the express provisions of that rule.
The majority seeks to support its conclusion by asserting that witness preclusion “is a severe sanction and should only be invoked when there has been serious misconduct by the party seeking modification-” Maj. op. at 751. The majority is wrong on both counts. Precluding a witness from testifying when that witness is not properly identified in a pretrial disclosure certificate, far from being the severe sanction the majority believes it to be, is instead a common practice. Indeed, federal circuit courts routinely decide that it is not an abuse of discretion to preclude witnesses from testifying at trial when those witnesses have not been properly identified in a pretrial order. See, e.g., Sexton v. Gulf Oil Corp., 809 F.2d 167 (1st Cir.1987); Napolitano v. Compania Sud Americana de Vapores, 421 F.2d 382 (2d Cir.1970); Ely v. Reading Co., 424 F.2d 758 (3d Cir.1970); Lirette v. Popich Bros. Water Transp., Inc., 660 F.2d 142 (5th Cir.1981); Campbell Indus. v. M/V Gemini, 619 F.2d 24 (9th Cir.1980); Grant v. Brandt, 796 F.2d 351 (10th Cir.1986).
Similarly, the majority is incorrect in asserting that witness preclusion is only justified when the failure to properly disclose a witness rises to the level of “serious misconduct.” The majority cites Freedman v. Kaiser Foundation Health Plan, 849 P.2d 811, 815 (Colo.App.1992), as support for this conclusion. Freedman did not address the question of witness preclusion but rather, it involved limiting the scope of an expert’s testimony. The court held that “[wjhether such a sanction should be imposed rests within the sound discretion of the trial court, and absent a clear abuse of that discretion, its determination will not be disturbed.” Id. at 815. Freedman says nothing about the appropriateness of witness preclusion as a sanction nor that serious misconduct is a prerequisite for imposing that sanction.
More important, however, is that by requiring that serious misconduct be shown as a prerequisite for ordering witness preclusion, the majority has ignored the express requirements of C.R.C.P. 16(b). As noted above, Rule 16 provides that a party, in seeking a supplemental endorsement of a witness, “shall set forth the subject matter of the expert’s testimony and state why the expert could not have been disclosed earlier.” Under the majority’s holding, a party could completely fail to comply with this provision and yet a trial court would be powerless to preclude the proposed witness from testifying unless the failure to make disclosure earlier amounts to serious misconduct. In short, the majority has written out of Rule 16 the mandatory requirements provided therein and in their place, has established that serious misconduct is required to preclude a *761witness from testifying regardless of whether the provisions of C.R.C.P. 16 have been complied with.
The majority has unnecessarily intruded on the ability of trial courts to exercise their discretion in managing cases. In my judgment, the micromanagement of pretrial discovery is not a proper role for this court.
Accordingly, I respectfully dissent.
I am authorized to say that Justice VOL-LACK joins in this dissent.
. Other relevant facts are set forth in the majority opinion, see maj. op. at 747-748 and thus, are not repeated here.
. The majority attempts to discount the breadth of its analysis by stating: "We do not believe, however, that a continuance gives a party free reign to reopen discovery. The requested discovery must still be necessary, requested in good faith, and the delay caused must not be prejudicial.” Maj. op. at 753 n. 10.
In my judgment, and in spite of this caveat, it is clear that the majority’s analysis essentially stands for the proposition that when a trial continuance is granted, parties may begin discovery anew so long as that discovery falls within the time limits imposed by C.R.C.P. 16 as to the new trial dates. As its analysis for each of the discovery motions at issue illustrates, there apparently will never be prejudice to an opposing party as a result of renewed discovery when a trial continuance has been granted. Furthermore, it seems unlikely that a party would seek additional discovery which is not, in some sense, "necessary.” Necessity apparently is to be equated with useful. See maj. op. at 752-757 (explaining why the testimony of Dr. Day, Dr. Pacey, Booth, Adams, and the four witnesses discovered as a result of Grooms' and Teachy's information will be useful to plaintiff’s case). Thus, based on its own analysis, the majority opinion stands as a repudiation of the purported limits of its holding.
. The trial court's order denying plaintiff's motion to endorse Dr. Day states, in part,
[C.R.C.P. 16] certainly does not contemplate the endorsement of an additional expert witness for the reason that the additional witness is a stronger witness than other experts that have already been endorsed. Plaintiff states in paragraph 9 of her motion that Dr. Day's testimony "is necessary in order for the Plaintiff to be able to present her case. Justice mandates [that] an expert with Dr. Day’s credentials who is not intimidated and who will not be intimidated set forth the facts for the jury’s consideration.”
. Though plaintiff's motion to endorse Booth and Adams was characterized as an attempt to “clarify” her disclosure certificate, the trial court appropriately concluded that "[u]se of the word 'clarify' will not gloss over the untimely attempt to endorse Adams and Booth. Plaintiff has always known of the involvement of Adams and Booth and has always known that the Defendants would take the position that 'there was nothing to indicate or cause suspicion that [the donor] carried the HIV virus.' "