The "ice" storm: problems with expert evidence on the effects of methamphetamine

There is growing community concern that methamphetamine (commonly known as Ice) is fuelling violent, erratic and criminal behaviour. Criminal prosecutions of Ice-fuelled defendants are on the rise. Scientific and medical expert evidence is being called upon in such criminal trials, to present the results of the defendant's blood-drug concentration and provide an opinion as to the effects of Ice on the defendant at the time of the alleged crime. Based on an analysis of recent case law and a summary of what science knows about the issue, the authors contend that any expert opinion about an accused person's likely behaviour, based on interpretations of blood-drug concentrations, are speculative and potentially prejudicial to the defendant. Such opinions should therefore be inadmissible. The authors argue for the introduction of a statutory reliability test as a way of ensuring that this unreliable expert evidence does not result in any miscarriages of justice.