However, the State could not attempt to impeach appellant by showing that the absent Bryant had previous convictions. Western Atlantic R. Co. v. Vaughn, 113 Ga. 354 (1) ( 38 S.E. 851) (1901); Cross v. State, 136 Ga. App. 400, 405 (6) ( 221 S.E.2d 615) (1975). "The trial court [erred] in allowing the [S]tate's attorney to cross-examine [appellant] as to whether [his companion] had `been [convicted of selling cocaine].' This evidence was not shown to be relevant to any issue in the case and must consequently be construed as an improper attempt to impugn [appellant's] character and establish his guilt by association.

The appellant failed to show prejudice by the exclusion of the questions asked on cross-examination. See Cross v. State, 136 Ga. App. 400, 409 (8) ( 221 S.E.2d 615) (1975) and cit. Enumeration of Error 1 is without merit. 2.

Alderman v. State, 241 Ga. 496, 510 ( 246 S.E.2d 642) (1978); Emmett v. State, 232 Ga. 110, 115 ( 205 S.E.2d 231) (1974). But see, Cross v. State, 136 Ga. App. 400, 402 ( 221 S.E.2d 615) (1975), stating, in dicta, that a truth-serum test would not be admissible in evidence and "if admitted in evidence it would have had no probative value." In determining whether a given scientific principle or technique is a phenomenon that may be verified with such certainty that it is competent evidence in a court of law, trial courts have frequently looked to see whether the technique has gained general acceptance in the scientific community which recognizes it. Frye v. United States, 293 F 1013 (D.C. Cir. 1923); Salisbury v. State, 221 Ga. 718 ( 146 S.E.2d 776) (1966).

His extraordinary motion for new trial was overruled by the trial court. Both these decisions were affirmed by the Court of Appeals in Cross v. State, 136 Ga. App. 400 ( 221 S.E.2d 615) (1975) and this court denied certiorari. Cross then filed habeas corpus petitions in federal court and relief was denied him both at the district court level and in the Fifth Circuit Court of Appeals. Two weeks later, Cross filed his petition for writ of habeas corpus in the DeKalb Superior Court alleging "newly discovered evidence."

It follows that defendant's conviction should be reversed. Polk v. State, 202 Ga. App. 738, 739 (2) ( 415 S.E.2d 506); Hall v. State, 180 Ga. App. 881, 882 (3) ( 350 S.E.2d 801); Richards v. State, 157 Ga. App. 601, 602 (2) ( 278 S.E.2d 63); Grant v. State, 142 Ga. App. 606, 607 ( 236 S.E.2d 691); Cross v. State, 136 Ga. App. 400, 405 (6) ( 221 S.E.2d 615); Corley v. State, 64 Ga. App. 841, 842 (3) ( 14 S.E.2d 121). I am authorized to state that Judge Cooper joins in this dissent.

The officer's testimony certainly does not come within any of the authorized methods for impeachment of a witness. See Cross v. State, 136 Ga. App. 400, 404-405 (5, 6) ( 221 S.E.2d 615) (1975); OCGA §§ 249-82 through 24-9-84. "This testimony had nothing to do with the case against the defendant.

"While a witness may be impeached by competent proof of conviction of a crime involving moral turpitude [cit.] this competent proof is the record of the witness' conviction or plea of guilty. It is not competent to prove by the witness that he entered a plea of guilty. [Cit.]" Cross v. State, 136 Ga. App. 400, 405 (6) ( 221 S.E.2d 615) (1975). "`A witness cannot be discredited even by his own testimony that he has been convicted of an offense involving moral turpitude; it is necessary to introduce an authenticated copy of the record of the court in which he was convicted.' [Cit.

This rule obtains even if the defendant's character is placed in issue and especially applies where the testimony is volunteered by a witness and not directly elicited by the prosecutor. Jones v. State, 167 Ga. App. 847, 848 ( 307 S.E.2d 735) (1983); Cross v. State, 136 Ga. App. 400 ( 221 S.E.2d 615) (1975). With regard to the similar crimes issue, there is no requirement that a previous offense be absolutely identical to the one being prosecuted so as to make it admissible, Millwood v. State, 164 Ga. App. 699 (1) ( 296 S.E.2d 239) (1982), nor does the lapse of time between the two stabbings automatically require the exclusion of such evidence.

"Ordinarily, when illegal testimony is placed in evidence, it is not an abuse of discretion to refuse to grant a mistrial if sufficient corrective instructions are given in ruling the testimony out. [Cits.] This is true . . . especially when the testimony is volunteered by the witness and not directly elicited by the [District Attorney]." Cross v. State, 136 Ga. App. 400, 403 ( 221 S.E.2d 615) (1975). Furthermore, any possible error was rendered harmless when appellant subsequently testified on cross-examination that he had consumed four beers the day of the automobile collision.

The grant or refusal of a mistrial is largely within the court's discretion. Manchester v. State, 171 Ga. 121, 137 ( 155 S.E. 11) (1930); State v. Abdi, supra; Cross v. State, 136 Ga. App. 400 ( 221 S.E.2d 615) (1975). A mistrial is not per se an acquittal barring a second prosecution.