On August 11,1978, the defendant, Ricky Dillon, was convicted of felony menacing. The court of appeals reversed the conviction because of the failure of the trial court to instruct the jury on the theory of self-defense. People v. Dillon, 631 P.2d 1153 (Colo.App.1981). We granted certiorari and now reverse the judgment of the court of appeals.
I.
At approximately 10:30 p.m. on December 22,1975, Margaret Driscoll drove into a gas station in order to purchase a package of cigarettes. At the same time, the defendant pulled into the station from the opposite direction. Driscoll testified that as she walked into the office the defendart told her to move her car, calling her a “white honky bitch.” Driscoll refused and went in to buy the cigarettes.
The defendant followed Driscoll into the office and twice tapped her on the shoulder, again telling her to move her car. Driscoll completed her purchase and agreed to move the car. She then called the defendant “a nigger” because she “was angry.” In response, the defendant struck her in the face two times.
Driscoll then went to her car, got a pipe, and began chasing the defendant. Although the sequence of events is not clear, it appears that a friend of Driscoll, William Decker, appeared and hit the defendant. The defendant then chased Decker.
*843Upon returning from the chase, the defendant asked Gregory Price, a passenger in his vehicle, for his “piece,” at which time he was given a handgun. The defendant confronted Driscoll with the gun and both agreed to cease further fighting. However, when Driscoll turned to walk back to her car, the defendant struck her on the head with the handgun.
Driscoll got into her car and sat behind the wheel dazed. The defendant continued to point the weapon at her, telling her to move. At this point, a friend of Driscoll who was a passenger in her vehicle, convinced Driscoll to leave the premises.
As a result of the altercation, the defendant was charged with felony menacing,1 assault in the second degree,2 and a crime of violence.3
Defendant was found guilty of felony menacing. The jury was unable to reach a verdict on the second-degree assault charge, and the court granted defense counsel’s motion for mistrial on that count. Subsequently, the district attorney requested that the court enter a nolle prosequi order on the second-degree assault and crime of violence charges. The court granted the request and sentenced the defendant on the felony menacing charge to an indeterminate term of imprisonment not to exceed five years. This sentence was to run consecutively to a life-imprisonment sentence he had received in another case.
II.
The jury returned the guilty verdict on August 11,1978. No motion for a new trial was filed within the time frame established by Crim.P. 33(b). The court entered judgment and sentenced the defendant on September 8,1978. Further, the court appointed a public defender for the purpose of appeal and allowed defendant’s court-appointed trial counsel to withdraw. A timely notice of appeal was filed on October 6, 1978. See C.A.R. 4(b). The notice stated that the appeal would be based upon grounds set forth in defendant’s motion for new trial.
Subsequently, the public defender, in prosecuting the appeal, realized that no new trial motion had been filed. On January 12, 1979, leave was requested to file a motion for new trial and a motion for judgment notwithstanding the verdict. The trial court denied the motions. On January 25, 1979, a notice of appeal was filed based upon the denial of leave to file the motion for new trial. This appeal was consolidated with the appeal challenging the defendant’s conviction.
On appeal, the court of appeals reversed. People v. Dillon, supra. It ruled that “the trial court abused its discretion when it denied defendant’s motion to file untimely motions and thereby perfect his appeal.” Id. at 1154. Further, it ruled that the trial court erred in refusing to instruct the jury on self-defense.
The People challenge the court of appeals’ decision on two grounds. They argue that the trial court properly denied defendant’s motion for leave to file motions out of time and properly refused to instruct the jury on self-defense.
The defendant argued before the court of appeals that the trial court erred in refusing to declare a mistrial after two jurors may have seen him being taken down the hall of the courthouse in handcuffs. The court of appeals did not address this argument because it reversed the conviction on other grounds. Given our disposition of this case, however, we will address defendant’s contention.
III.
The People first argue that the trial court correctly denied the defendant’s request to file motions out of time. We agree.
Crim.P. 33(b) provides in part:
*844“A motion for a new trial other than on the ground of newly discovered evidence shall be filed within fifteen days after verdict or finding of guilt or within such additional time as the court may fix during the fifteen-day period.”
The language of the rule clearly specifies that the trial court may only extend the time for filing “during the fifteen-day period.” In the present case the motion to allow the filing out of time was not presented until more than five months following the jury verdict and more than four months after the entry of judgment and sentencing in the case.
Defendant argues that relief from a failure to timely file any motion or to ask for an extension within the time prescribed for filing a motion may be afforded pursuant to Crim.P. 45(b). He further contends that the trial court erred in neglecting to apply the standards set out in Rule 45. Rule 45(b) provides:
“When an act is required or allowed to be performed at or within a specified time, the court for cause shown may at any time in its discretion:
(2) Upon motion, permit the act to be done after expiration of the specified period if the failure to act on time was the result of excusable neglect.”
In Colorado the filing requirements set forth in Rule 33 are thus tempered by Rule 45. People v. Moore, 193 Colo. 81, 562 P.2d 749 (1977). The trial court may allow the filing of a motion for a new trial outside of the time limits provided in Crim.P. 33(b). Nevertheless, the burden of showing excusable neglect is upon the defendant; further, the granting of the relief is within the sound discretion of the trial court. People v. Moore, supra.
There is always, of course, the requirement that the court have jurisdiction to act. It is axiomatic that any action taken by a court when it lacked jurisdiction is a nullity. McLeod v. Provident Mutual Life Insurance Co., 186 Colo. 234, 526 P.2d 1318 (1974). We are thus faced with the question of whether the trial court was divested of jurisdiction once the notice of appeal had been filed, leaving the trial court powerless to grant the motion for new trial. We believe that the trial court had no power to grant the motion for a new trial. See William F. Larrick, Inc. v. Burt Chevrolet, Inc., 147 Colo. 133, 362 P.2d 1030 (1961); Brooke v. People, 139 Colo. 388, 339 P.2d 993 (1959). See also People v. Jones, 631 P.2d 1132 (Colo.1981); Kurtz v. People, 177 Colo. 306, 494 P.2d 97 (1972).
In Brooke v. People, supra, we held that where an appeal was pending before us, “jurisdiction of the case was vested entirely in this court, and the trial court had been divested of all jurisdiction in the cause other than to prepare and certify the record to this court in accordance with the applicable statute.” 139 Colo, at 394, 339 P.2d at 996. We believe this reasoning equally applicable to the case at hand. The efficient administration of justice would not be served by a rule that permitted the trial court to reconsider its earlier rulings at the same time that an appeal is pending in an appellate court. Unless otherwise specifically authorized by statute or rule, once an appeal has been perfected, the trial court has no jurisdiction to issue further orders in the case relative to the order or judgment appealed from.4 Consequently, should it be necessary for the trial court to act, other than in aid of the appeal or pursuant to specific statutory authorization, the proper course would be for a party to obtain a limited remand from the appellate court. See People v. District Court, 638 P.2d 65 (Colo.1981).
In light of the foregoing, we do not believe the trial court abused its discretion in failing to grant a motion for new trial, because in our view, it had no discretion to exercise. As a result, our review of defendant’s contentions on appeal is under the *845“plain error” standard. Crim.P. 33(a), 52(b).
IV.
We must now consider whether the trial court’s refusal to give the defendant’s requested self-defense instruction was plain error. That is, we must decide whether it was a grave error that seriously affected the substantial rights of the accused. People v. Barker, 180 Colo. 28, 501 P.2d 1041 (1972). In order for us to find plain error, there must be a reasonable possibility that the alleged erroneous instructions contributed to the defendant’s conviction. People v. Aragon, 186 Colo. 91, 525 P.2d 1134 (1974). The existence of this possibility must be determined by an examination of the particular facts of the case: People v. Mills, 192 Colo. 260, 557 P.2d 1192 (1976).
The general rule in Colorado is that an instruction embodying the defendant’s theory of the case must be given if there is any evidence in the record to support it. People v. Griego, 183 Colo. 419, 517 P.2d 460 (1973); People v. Moya, 182 Colo. 290, 512 P.2d 1155 (1973); People v. Montagne, 181 Colo. 148, 508 P.2d 388 (1973). This is so, no matter how improbable or unreasonable defendant’s theory is. For example, in People v. Moya, supra, the defendant was charged with attempted burglary and gave a highly implausible explanation on the witness stand of how he came to be at the scene. We held that because there was some evidence in the record (i.e., his testimony) to support the defendant’s theory of the case, it was reversible error for the trial court to refuse to give the requested instruction.
In the case before us, however, there is not a scintilla of evidence in the record to support a self-defense instruction. Apparently, defendant’s contention is that Driscoll’s chasing him with the aluminum pipe before he pointed the gun at her or hit her with it would have justified his using physical force to defend himself pursuant to section 18-1-704, C.R.S.1973 (1978 Repl.Vol. 8), which recognizes a right of self-defense. Although section 18-1-704 negates the right of an “initial aggressor” to use physical force in his defense, the defendant argues that the jury should have been given the self-defense instruction and been allowed to determine, as a matter of fact, the question of initial aggression.
We disagree with defendant’s contention under the circumstances of this case. That defendant struck Driscoll first is uncontro-verted by any evidence in the record. Moreover, all the testimony indicates that Driscoll was struck from behind as she was walking back to her car after Driscoll and Dillon agreed not to fight anymore, and then Dillon again pointed the gun at her when she was back in her car. Furthermore, the defendant’s theory of the case, as it developed through the examination and cross-examination of witnesses and in closing arguments, was that the defendant had been misidentified and that it had in fact been Mr. Price, the passenger, who had brandished the weapon.
Were we to hold that a self-defense instruction should have been given on the facts of this case, such an instruction would be necessary in virtually every case where force or the threat of force is used. We decline to impose such a requirement. Consequently, we conclude that any error, if indeed there was error, was clearly not plain error.
V.
Finally, we must address the defendant’s contention that the trial court erred in refusing to grant a mistrial because of possible prejudice from the defendant’s being escorted handcuffed down the hall of the courthouse past some jurors who were standing in the hall. We do not believe there was error.
The incident occurred on the morning of the second day of trial, as the defendant was being brought from the central holding cell to a holding cell near the courtroom. The defendant was dressed in civilian clothing and had his hands cuffed behind his back. As the defendant and a deputy sheriff were walking down the hall, two members of the jury walked out of the jury *846room into the hall. The deputy testified in camera that his body was between the defendant and the two jurors and that he did not believe that the jurors could have seen the handcuffs. Defense counsel stated that he did not want the jurors to be questioned about what they had seen; he asked only for a mistrial.
We have often stated that “the presumption of innocence requires the garb of innocence” and that “every defendant is entitled to be brought before the court with the appearance, dignity, and self-respect of a free and innocent man, except as the necessary safety and decorum of the court may otherwise require.” See, e.g., Eaddy v. People, 115 Colo. 488, 492, 174 P.2d 717 (1946). Consequently, in Eaddy it was held improper to bring the defendant into court wearing coveralls with the words “County Jail” written in large letters across the back. Similarly, in the absence of necessity, a defendant should not be brought into court manacled. Montoya v. People, 141 Colo. 9, 345 P.2d 1062 (1959).
The mere fact of exposure of a handcuffed defendant is not necessarily sufficient to warrant the granting of a mistrial, however. For example, in Scott v. People, 166 Colo. 432, 444 P.2d 388 (1968), under circumstances quite similar to those in the case before us, we held that a probability of inadvertent exposure of handcuffed defendants to jury members in the hall of the court building was not reversible error. We stated:
“More than one defendant has escaped from a courthouse in Colorado where the defendant was being moved from the holding room of the building to the courtroom door without handcuffs. Anytime a defendant is moved from room to room in a public building there is some element of risk to the public in the event of an attempted escape which must be balanced with the rights of the defendant to be brought before the court without handcuffs unless there is some great necessity to do otherwise.”
166 Colo, at 441, 444 P.2d at 392-93.
Similarly, in McLean v. People, 172 Colo. 338, 473 P.2d 715 (1970), we held that inadvertent exposure of a handcuffed defendant to two jurors in the hallway was not a ground for reversal absent a showing that the exposure was unnecessary and prejudicial to the defendant. See also People v. Cardwell, 181 Colo. 421, 510 P.2d 317 (1973) (where there was no evidence that any jurors saw the defendant being transported in handcuffs and defendant did not request permission to question jurors, no reversible error); Hamrick v. People, 624 P.2d 1320 (Colo.1981).
In order for us to conclude that the incident in the case before us constituted reversible error, we would have to find that the exposure was both unnecessary and prejudicial. The trial court found that it was unexpected that the jurors would have been out in the hall at that time, that the sheriff had taken all reasonable precautions, and that there was no prejudice to the defendant. Considering the need for security, the fact that it was not demonstrated that the jurors had seen the defendant handcuffed, and the inadvertent nature of the exposure, we are not prepared to say that the trial court erred in denying the defendant’s motion for a mistrial.
The judgment of the court of appeals is reversed.
QUINN, J., dissents, and DUBOFSKY, J., joins in the dissent.. Section 18-3-206, C.R.S.1973 (now in 1978 Repl.Vol. 8).
. Section 18-3-203(l)(b), C.R.S.1973 (now in 1978 Repl.Vol. 8).
.Section 16-11-309, C.R.S.1973 (now in 1978 Repl.Vol. 8).
. Cf. People v. Small, 631 P.2d 148 (Colo.1981), (where trial court severed speedy trial issue from new trial motion to allow defense counsel to testify about it, trial court had jurisdiction to consider speedy trial issue under Crim.P. 35 even though appeal was pending).