Throughout 2011, the phone hacking scandal has rocked the UK’s public landscape, drawing comparisons with Watergate in terms of its effect on our national psyche and its long-term significance. The saga has kicked off again this Autumn with the Leveson Inquiry, but listening to testimony of News Corporation staff throughout the year one would be forgiven for asking, 'what's the point of a public inquiry if its participants refuse to answer questions, purportedly to avoid prejudicing ongoing criminal investigations?'.

As the scandal has unfolded, the frequent refrain at parliamentary hearings is that witnesses are refusing to answer questions because they do not wish to prejudice ongoing criminal investigations. That response is understandable. Answers given at a preliminary stage of a criminal investigation could interfere with other witnesses, could constitute or could lead to the concealment or destruction of evidence, and could even raise false allegations of criminal conduct - all potentially offences in and of themselves, constituting perversion of the course of justice or other crimes. A witness would be well within their rights not to answer certain problematic questions under oath. But those are very likely the very same questions which go to the heart of our understanding of these events, raising real concerns about the timing and purpose of criminal investigations and of parallel public inquiries.

The purpose of a criminal investigation is to determine if police and prosecutors can properly ascribe fault, as opposed to a broader search for the truth. Trials are based on probabilities, not certainties; juries are asked to be sure of guilt, not absolutely certain of it, nor can juries return verdicts against un-indicted persons. By contrast, the purpose of public inquiries is very much to get as close to the truth as any judicial process can. Inquiries often seek to lay the specifics of blame to one side, though the evidence gathered during the process can lead to blame subsequently arising; whether to prosecute soldiers with whom fault was found by the Bloody Sunday Inquiry, for example.

The problems of both processes running in parallel are exacerbated where, as here, both processes are urgently necessary, and where there has apparently been a criminal investigation in one form or another since at least 2007, which has failed to produce results matching the scale of the scandal now unfolding.

There will be a natural tendency to want to deal with all aspects of the phone hacking scandal at once. The public demands both answers, and that someone or something be responsible for what has happened. The hacking of the phones of murdered schoolchildren and of veterans who died for their country demands no less. But although frustrating, it may be necessary to prioritise one process over the other in the short term. Do we want the truth, or do we want to assign fault? It may be that we simply cannot do both at once.

Nicholas Cropp is a barrister at 7 Bedford Row and specialises in Complex Fraud, Commercial Crime, Public & Regulatory Law