Here's a link to a book by Anthony Walsh & Lee Ellis, "Criminology: an Interdisciplinary Approach" and it includes a discussion on IQ. It mentions a 9-14 point gap in IQ between offenders and non-offenders. However, only a 1 point difference between less serious offenders and non-offenders compared to 17 points between serious persistent offenders and non-offenders.,M1

The part I found most interesting was in the section of "Intellectual Imbalance". The imbalance is when there is a 12 point difference between VIQ and PIQ. Criminals are significantly more likely to have a VIQ<PIQ imbalance.