The rule of law means less if it is being constantly overturned  Respect for the law will diminish if criminal verdicts exist in a perpetual state of uncertainty. We need to be protected from the state in other ways, too - from the vindictive or obsessed policeman that will pursue a case because he 'knows' the accused, properly acquitted in a court of law, to be guilty nevertheless. The nature of our police force means that these instances are inevitable as it imparts a strong cognitive bias onto our policemen to look for guilt - so unless we mandate a rule determining when a line of investigation has to end, police will continue to focus on their chosen 'perpetrator' until they get the result that they have decided is correct. As Matthew Kelly QC notes, removing double jeopardy restrictions could 'lead to prosecutions routinely seeking a second bite of the cherry, if a case flopped first time for good reason.'1  Given that we are talking about a tiny proportion of cases, it is better to have the principle of finality - because the police will spend vast amounts of time and effort and money on case that are already resolved, to the detriment of crimes that will receive less attention. Therefore successful detective work, and subsequent conviction rates, will increase with the double jeopardy rule in place, not decrease, for police cannot allow themselves to remain rooted in closed cases. 1 BBC News. (2005, April 3). Double jeopardy law ushered out. Retrieved May 12, 2011, from BBC News: