Where no legal necessity exists for the court’s sua sponte declaration of a mistrial, double jeopardy attaches so as to bar retrial. Once a defendant is placed on trial in a court of competent jurisdiction, on a valid accusatory pleading, before a jury duly impaneled and sworn, a discharge of that jury without a verdict is equivalent in law to an acquittal and bars a retrial, unless the defendant consents to the discharge or legal necessity requires it. Here, the trial court in a murder trial found that defense counsel was ineffective for failing to suppress defendant’s statement and after the jury had heard about a third of the defendant’s tape recorded statement to the police, as requested by the defense, the court declared a mistrial. As part of trial strategy, counsel had presented the statement, believing its value as a defense outweighed its coerced nature. The trial court, believing that it should have been suppressed, declared a mistrial. The prosecution claimed that retrial was not barred because legal necessity required the mistrial. The appellate court disagreed, noting that under California law, legal necessity is more limited than federal law and ineffective assistance of counsel does not ordinarily constitute legal necessity and is found only in extreme circumstances which did not exist here. Instead of declaring the mistrial sua sponte, the court should have let the trial continue and if defendant was convicted, entertain a motion for a new trial based on ineffective assistance of counsel.