‘Science and justice’ investigates the relationship between the universal nature of science, and the local nature of the law. Forensic evidence is often presented in the courtroom by expert witnesses. The UK legal system states that these witnesses need ‘expertise’, but no criteria exist to define what level this expertise needs to be at. In the United States two tests are used to determine whether expert evidence is admissible. These determine whether the evidence is based on ‘scientific knowledge’ and whether it is generally accepted by the scientific community, but they also bring about their own issues. The development of an effective relationship between science and law is essential to ensure science continues to contribute to criminal justice.