I'm with drmonica on this one, in that a preponderance of prisoners in the system are poorly educated--sometimes, I'm sure, because of a lower IQ, but also because of a particular socio-economic status, family problems, bad friends, mental illness, learning disabilities, or whatever else might cause people to do poorly in school. This one factor, the lack of education, generally creates the kinds of problems which can get one incarcerated. To pin the blame solely on low IQs is absolutely beyond outrageous and certainly can not be proven definitively. There are just too many other contributing factors which would prevent such a conclusion.
No. There is very little conclusive data on anything related to IQ or delinquency. What there is out there, however, is a mountain of evidence of correlation when one examines the factors leading to delinquency.
Jails and prisons are filled with prisoners who did not do well in school. The majority of these prisoners, if tested academicallly, do not read well, have emotional/behavioral disorders, and/or experienced symptoms of special education needs that may or may not have been addressed by their schools.
I believe that there is a strong correlation between IQ and delinquency, in my professional educator's opinion. However, there is not strong conclusive evidence of it.
It seems that the greater problem lies with society rather than the individuals themselves. If society was better at acknowledging, rewarding and finding meaningful roles for those who aren't necessarily high on the IQ rating, then perhaps so many people wouldn't be driven to delinquency.
I wouldn't say there is conclusive data that establishes a causal relationship between low IQ and delinquency. There is certainly a mountain of empirical data to suggest a link, however. The degree to which low IQ actually causes the delinquent behavior seems to depend on who you ask and which study you believe.
Many researchers (see links below) seem to suggest that people with low IQs, especially males, tend to be less successful in school and therefore have a greater risk of resorting to criminal behavior, and at younger ages. That is, they suggest it is not the IQ per se that causes the behavior, but the poor socialization people often receive as a result of the lower IQ.
There seems to be some evidence to suggest that those with low IQs are less likely to link consequences with behavior in their decision making processes, and therefore are more likely to commit crimes of all types, including violent crimes. Again, though, I wouldn't say there is a consensus, so follow the links and draw your own conclusions as to which theory is most well proven.
An interesting Link= DISORGANIZED CRIME: LEARNING DISABILITY AND THE CRIMINAL JUSTICE SYSTEM by Nancy Cowardin, Ph.D. On page 6 DIFFERENTIAL TREATMENT explains it very clearly.