A "Molineaux hearing" refers to a pre-trial hearing on the admissibility of evidence of prior uncharged crimes by the defendant in a criminal trial. In most cases evidence of prior uncharged crimes is not admissible because of its potential prejudicial effect. Under certain circumstances it may be admissible. If the prosecutor wishes to bring in evidence of prior uncharged crimes he requests a Molineaux hearing. The judge decides if the evidence is admissible.