The study undermines the argument put by the police that the retention of the right to silence allows guilty people to escape justice. The Royal Commission is expected to make a recommendation on reform of the right to silence in its report in June.
The research, by Roger Leng, of the Law Faculty at the University of Birmingham, concludes: 'Reform of the right to silence . . . would have a limited effect in enhancing the prospects of convicting guilty offenders in only a very small proportion of cases.'
Mr Leng says in more than 1,000 cases the right to silence was used in only 5 per cent, with convictions in roughly half. This suggests the conviction of a guilty person could have been hampered in 2 or 3 per cent of cases.
In 10 per cent of acquittals and cases dropped before to trial, the defendant was silent during interrogation. But the majority failed for unconnected reasons.
Concern about 'ambush' defences by suspects who have remained silent is misplaced, he says. True 'ambush' defences are rare and mostly due to the failure of police to allow suspects to explain their defence.