The trial court granted the state’s motion for a mistrial in Ivan Edward Smith’s jury trial for murder, felony murder, and aggravated assault. The mistrial was declared after Smith testified on redirect examination by defense counsel that the custodial statement he gave to police had been coerced. ^[1] The trial court stated that such an allegation should have been raised in a Jackson-Denno hearing, and that she could not “cure the defendant’s testimony about [the statement being forced] because he said it several times.” Prior to retrial for the same offenses, Smith filed a plea of former jeopardy seeking to bar[*783] the second prosecution. The trial court denied the plea in bar. We reverse.

1. “Once [Smith’s] jury was impaneled and sworn, jeopardy attached, and he was entitled to be acquitted or convicted by that jury.” Morris v. State, 262 Ga. 446, 447 (421 SE2d 524) (1992). If a mistrial is declared without a defendant’s consent or over his objection, the defendant may be retried only if there was a “manifest necessity” for the mistrial. Jones v. State, 232 Ga. 324, 327 (206 SE2d 481) (1974); see also OCGA § 16-1-8 (a) (1). At a minimum, the mistrial in this case was without Smith’s consent, and could be considered over his objection. ^[2]

A manifest necessity to declare a mistrial may exist “under urgent circumstances,” United States v. Perez, 22 U. S. 576 (6 LE 165) (1824), such as where “an impartial verdict cannot be reached, or [where] a verdict of conviction could be reached but would have to be reversed on appeal due to an obvious procedural error in the trial,” Illinois v. Somerville, 410 U. S. 458, 464 (93 SC 1066, 35 LE2d 425) (1973). Because of “ ‘the severe consequences of ordering a mistrial without the accused’s consent,’ [cit.],” Cherry v. State Bd. of Corrections, 613 F2d 1262, 1266 (5th Cir. 1980), a trial court should give careful, deliberate, and studious consideration to whether the circumstances demand a mistrial, with a keen eye toward other, less drastic, alternatives, calling for a recess if necessary and feasible to guard against hasty mistakes, see id.

2. The state contends that Smith repeatedly injected irrelevant and prejudicial matters in the trial despite instructions from the court, ^[3] see Miller v. State, 204 Ga. App. 562, 565 (420 SE2d 12)[*784] (1992), making a mistrial necessary to ensure that both Smith and the state receive a fair trial, see Abdi v. State, 249 Ga. 827, 828 (294 SE2d 506) (1982).

(a) First, we note that the lack of a Jackson-Denno hearing with respect to Smith’s custodial statement did not make a mistrial necessary. Absent a proper objection to a statement’s admission, due process does not require a separate hearing as to the voluntariness of the statement. Wainwright v. Sykes, 433 U. S. 72, 86-91 (97 SC 2497, 53 LE2d 594) (1977). See also Dent v. State, 243 Ga. 854 (2) (257 SE2d 241) (1979); McNair v. State,^ 190 Ga. App. 412 (2) (379 SE2d 424) (1989). Smith did not complain about the admission of the custodial statement at any time before or after it was presented to the jury because, according to Smith, the statement supported his justification defense. Even when Smith testified that he felt coerced when he gave the statement, he did not claim that the statement should not have been admitted into evidence. As Smith did not complain about, and in fact desired, the statement’s admission, a Jackson-Denno hearing was not required to ensure that Smith received a fair trial, Wainwright, supra, and the failure to hold such a hearing was not an “obvious procedural error” or a threat to an impartial verdict creating a “manifest necessity” for a mistrial.

(b) Furthermore, a mistrial was not necessary because of the introduction of Smith’s testimony regarding the taking of his statement.

[T]he circumstances surrounding the taking of a confession can be highly relevant to . . . the purely legal question of its voluntariness, . . . [but] can also be of substantial relevance to the ultimate factual issue of the defendant’s guilt or innocence.

Crane v. Kentucky, 476 U. S. 683, 689 (106 SC 2142, 90 LE2d 636) (1986). “[E]vidence about the manner in which a confession was secured will often be germane to its probative weight.” Id. at 688. Furthermore, “the Constitution guarantees criminal defendants ‘a meaningful opportunity to present a complete defense.’ ” (Citations omitted.) Id. at 690.

We find that evidence regarding the circumstances surrounding[*785] Smith’s custodial statement was relevant to the probative value of the statement, either as a whole or in part. Smith could desire the custodial statement’s admission because it supported his justification defense, yet at the same time want the jury to be aware of the environment under which it was obtained. Based on evidence of a coercive environment, the jury could have chosen to give no weight whatsoever to the statement, thus discounting a major part of the state’s case. Therefore, as Smith’s testimony was relevant and should have been admitted to ensure Smith the “opportunity to present a complete defense,” id., we find that there was no manifest necessity for a mistrial based on Smith’s testimony.

Judgment reversed.