The current law governing the admissibility of expert evidence in criminal trials is unsatisfactory. If the reliability of expert evidence is in question, there are no clear guide lines for determining whether or not it is sufficiently trustworthy to be considered by the jury. In this consultation paper, the Law Commission makes provisional proposals for reform and poses some questions for consultees. Expert evidence, particularly scientific evidence, can have a very persuasive effect on juries. It is vital that such evidence should be used only if it provides a sound basis for determining a defendant’s guilt or innocence. There have been miscarriages of justice in recent years where prosecution expert evidence of doubtful reliability has been placed before Crown Court juries. There may also have been unwarranted acquittals attributable to such evidence. The Commission wants to ensure that the criminal courts have the means to authenticate expert evidence and be satisfied that the information before them is sound. It therefore proposes a new test for determining whether expert evidence should be admitted in a criminal trial. It also recommends new guidelines for Crown Court judges and magistrates’ courts to help them determine whether expert evidence is sufficiently reliable to be admitted.