I hate to say it but it could very well be that they didn't want anyone to break and run before they could get something on them.
Why they were not at least followed or matched for fingerprints or the DNA found in DVD's room I have no idea. Usually what you see is if the person is on probation or parol they can hold them for a possible violation and ask them questions, that I belive might have been a good idea for some.
Where are the good journalists...I know there are some.