Why write a book about the search for truth in the criminal justice process? Surely it is the purpose of any criminal justice system to arrive at the truth? Surely any defensible process must ensure that innocent people are not convicted and punished for a crime that they did not commit and that conviction and punishment are reserved for those who offend? There is, though, an implicit – and potentially dangerous – assumption that our criminal justice process, or indeed any other, can fulfil this task. If procedural reforms are suggested, they should – one hopes – be driven and judged against whether they would expedite truth-finding. To this end, one of the critical tasks that this book attempts to perform is to explore ways in which current procedure could be improved either to minimize the risk that innocent people are convicted or, on occasion, to increase the likelihood that those who offend are convicted. This, though, is only part of the purpose of the book.

A second aim is to recognize openly that the search for truth can conflict with other legitimate values and purposes. Take the example of an illegal search that yields incriminating evidence. Prioritizing truth would favour using such evidence to aid conviction, assuming that society benefits from the conviction and punishment of criminals, a notion some challenge. Yet, ignoring the context in which evidence was obtained threatens other values important to society. Individuals have human rights protections, notably in this context the right to a fair trial. These rights would be of little value if someone whose rights were infringed had no recourse. Excluding improperly obtained evidence may on occasion result in a factually guilty person being acquitted, but perhaps the need to preserve the integrity of the fact-finding process justifies this outcome. Truth may not always trump all other concerns, even if, as here, there is a potentially undesirable trade-off.

Our final broad theme is to question whether traditional criminal justice processes are equipped to discern the truth surrounding a criminal event. Perhaps society is simply expecting too much. Most crimes are not solved.