Lee Walker was indicted and convicted of the offense of aggravated assault, for that he shot through a door at Jacob Reese and wounded him in the hand and arm to the extent that it had to be amputated. He appeals, enumerating as error (1) the overruling of his motion for new trial on the general grounds, (2) allowing the prosecutor to remain in the courtroom, sequestration having been invoked, and to testify after other witnesses had done so, (3) denial of a mistrial because of an expression of opinion as to guilt by the District Attorney in his opening statement, (4) refusal to allow defendant to make an unsworn statement, the offense having occurred prior to the repeal of the unsworn statement law by amendment of Code Ann. § 38-415 and tried afterward, and (5) a charge that the jury might, in considering the defendant’s sworn testimony, take into consideration the fact that he was interested in the outcome of the case, as well as his demeanor and conduct while on the stand. Held:
1. The general grounds are without merit.
2. The district attorney requested of the court that the prosecutor be allowed to remain in the courtroom to assist in the presentation of the case. "It has been repeatedly held that it is within the discretion of the trial judge to permit a witness to remain in the courtroom to assist either the state or the accused, and while it is better that the witness should be first examined, this, too, is a matter of discretion, and the action of the court in these respects will not be reviewed. Carter v. State, 2 Ga. App. 254 (58 SE 532); Shaw v. State, 102 Ga. 667 (29 SE *275477).” Benton v. State, 9 Ga. App. 291 (6) (71 SE 8). Accord: Dye v. State, Ga. 220 113, 114 (2) (137 SE2d 465); Sparks v. State, 121 Ga. App. 115 (3) (173 SE2d 239).
3. In his opening statement to the jury the district attorney asserted "He [the judge] will tell you what the law is, and you are supposed to apply the law to the facts that have been presented to you, but I really and truly believe that you are going to find that he [the defendant] was not justified in blowing a man’s hand off or the lower part of his arm off, and that he was under some kind of reasoning . . to which counsel for the defendant interposed objection and moved for a mistrial on the ground that it was improper for the district attorney to state his personal opinion as to the guilt or innocence of the defendant.
The court admonished the jury to disregard this statement of the district attorney, informed them that while the district attorney had the right to state what the state expected to prove and what he believed the evidence would justify to the jury in drawing certain inferences, but that he was not permitted to assert a personal belief as to the defendant’s guilt, and that it was wholly a prerogative of the jury to decide the matter of guilt or innocence from the facts as proven; that they were not to be influenced in any expression of personal opinion by counsel and that it was to be utterly disregarded, and thereupon denied the motion for mistrial.
"[T]his court has repeatedly held that if the trial judge acts immediately, and in the exercise of his discretion takes such action as in his judgment prevents harm to the accused as a result of such improper statements, a new trial will not be granted unless it is clear that such action failed to eliminate from the consideration of the jury such improper statements. Brown v. State, 148 Ga. 264, 266 (96 SE 435); Johnson v. State, 150 Ga. 67 (1) (102 SE 439); Waller v. State, 164 Ga. 128 (4) (138 SE 67). Nelson v. State, 187 Ga. 576, 583 (1 SE2d 641); Spell v. State, 225 Ga. 705, 708 (171 SE2d 285). See also Moore v. State, 228 Ga. 662, 664 (187 SE2d 277).” Howard v. State, 229 Ga. 839, 840 (195 SE2d 14). As in those cases, no abuse of discretion appears here.
*2764. The crime is alleged (in the indictment) to have been committed April 2, 1973. The unsworn statement law was repealed by Ga. L. 1973, p. 292, amending Code Ann. §§ 26-401 (a), 27-405, and 38-415, effective July 1, 1973. This trial was held August 7, 1973. When the state concluded the introduction of its evidence and rested defendant’s counsel sought to put the defendant up for making an unsworn statement, contending that since the crime was alleged to have been committed prior to the effective date of the law abolishing unsworn statements, the abolition did not apply to the defendant.
The trial judge observed that in his view the change made by Ga. L. 1973, p. 292 was procedural only, and that it did apply to the present situation so that the defendant had only two options, one being to remain silent — which could not be held against him, and the other to take the stand, be sworn and testify as a witness. Under objection and protest the defendant elected to testify, and did. This ruling by the trial judge is enumerated as error.
If the change effected by Ga. L. 1973, p. 292 was procedural only and did not alter the situation to the disadvantage of the accused, the ruling of the trial judge was correct.
A similar situation arose when the bifurcated trial was introduced into our criminal procedure, and an accused whose offense was alleged to have been committed prior to the effective date of that Act objected to trial of his case under it, asserting that he had the right to proceed under the law as it had existed when the offense was committed. Our Supreme Court, in Todd v. State, 228 Ga. 746 (187 SE2d 831), after an excellent research of the problem raised, held that the change was procedural only and application of the new procedure did not violate the ex post facto principle.
In Todd, supra, the court relied on and quoted approvingly from People v. Ward, 50 Cal. 2d 702 (328 P2d 777, 76 ALR2d 911); Thompson v. Utah, 170 U. S. 343 (18 SC 620, 42 LE 1061) and Thompson v. Missouri, 171 U. S. 380, 387 (18 SC 922, 43 LE 204), all of which were criminal cases dealing with the issue of whether an Act which is procedural in nature violates the ex post facto rule when applied to a previously committed offense. *277These cases hold that there is no violation unless it results in the infliction of greater punishment for the crime or "alters the situation of the accused to his disadvantage.”
The disadvantage test is found in Thompson v. Missouri, supra:" '[W]e cannot perceive any ground upon which to hold a statute to be ex post facto which does nothing more than admit evidence of a particular kind in a criminal case upon an issue of fact which was not admissible under the rules of evidence as enforced by judicial decisions at the time the offense was committed. The Missouri statute, when applied to this case, did not enlarge the punishment to which the accused was liable when his crime was committed, nor make any act involved in his offense criminal that was not criminal at the time he committed the murder of which he was found guilty. It did not change the quality or degree of his offense. Nor can the new rule be characterized as unreasonable—certainly not so unreasonable as materially to affect the substantial rights of one put on trial for crime. The statute did not require "less proof, in amount or degree,” than was required at the time of the commission of the crime charged upon him. It left unimpaired the right of the jury to determine the sufficiency or effect of the evidence declared to be admissible, and did not disturb the fundamental rule that the state, as a condition of its right to take the life of an accused, must overcome the presumption of innocence, and establish his guilt beyond a reasonable doubt.’ ” These same things can be said of the Act abolishing the unsworn statement. It does not change the character of the offense charged, or the punishment which may be imposed. It does not lessen the burden of proof resting upon the state. It does not alter the rules of evidence (the unsworn statement is not evidence or controlled by the rules of evidence. Prater v. State, 160 Ga. 138 (2) (127 SE 296)).
The accused has no vested right in procedural matters. "A party has no vested right in a defense based upon an informality not affecting his substantial equities . . . there is no such thing as a vested right to do wrong.” Bullard v. Holman, 184 Ga. 788 (193 SE 586, 113 ALR *278763); Darby v. Cook, 201 Ga. 309, 311 (39 SE2d 665). "[F]or the purpose of operating on the remedy only, the Legislature may, undoubtedly, pass Retrospective Acts; and for such purposes, they are not unconstitutional.” Knight v. Lasseter, 16 Ga. 151, 153. "The procedures of courts are always subject to legislation. The amended Act of 6th December, 1880, repealed the ten days’ limitation of the 4161st section of the Code, and the duty and direction it imposed ceased to exist.” Willis v. Fincher, 68 Ga. 444. And so here, the Act of 1973, when it became effective on July 1 of that year simply caused the procedure of making an unsworn statement by defendants in criminal cases to cease to exist, and substituted the procedure of sworn testimony.
5. Error is enumerated upon a portion of the charge relating to the testimony of the defendant in which the court instructed: "You have the right to take into consideration the fact that he is interested in the result of the prosecution, as well as his demeanor and conduct on the witness stand.” We find no error. "The jury would be authorized to give his testimony such weight and credit as that of any other witness.” Williams v. State, 223 Ga. 773, 775 (4) (158 SE2d 373). Accord, Hogan v. State, 221 Ga. 9, 12 (142 SE2d 778). "[W]hen [the accused] does so testify [he] at once becomes the same as any other witness, and [his] credibility is to be tested by and subjected to the same tests as are legally applied to any other witness; and in determining the degree of credibility that shall be accorded to [his] testimony the jury have a right to take into consideration the fact that [he] is interested in the result of the prosecution, as well as [his] demeanor and conduct upon the witness stand . . .” Hudson v. State, 108 Ga. App. 192, 199 (4) (132 SE2d 508, 100 ALR2d 1395), cited approvingly in Hogan v. State, 221 Ga. 9, 12, supra, and in Mitchell v. State, 121 Ga. App. 382 (173 SE2d 709).
This interest of a witness in the result of the matter on trial, whether civil or criminal in nature, or lack thereof, is a matter which the jury is always authorized to consider in passing upon his credibility (Detwiler v. Cox, 120 Ga. 638 (48 SE 142); Zetterower v. State, 87 Ga. App. 24 (73 SE2d 88)), and it is especially true where the *279witness is himself a party to the cause. Smith v. Davis, 203 Ga. 175 (3) (45 SE2d 609). It is not error for the court to so instruct.
Submitted February 6, 1974 Decided June 14, 1974 Rehearing denied July 5, 1974 Guy B. Scott, Jr., for appellant. Harry N. Gordon, District Attorney, for appellee.Judgment affirmed.
Bell, C. J., Pannell, P. J., Quillian, Clark, Stolz and Webb, JJ., concur. Evans, J., concurs in part and dissents in part. Deen, J., concurs with dissent as to Enumeration of error No. 1.