I want to look up a couple of people and search their criminal history, if they have one.  

All the sites I have tried so far give just the basics and then want to charge for more details.

Is there a site that I can use that will do all this for free?

I don't know of any free sites and the pay sites are simply worthless whether you pay or not.  I once paid the money for a background check on myself and the results were laughable.  Pages and pages of shit I never did and once I filtered out all the crap it only showed about 1/4 of the times that I was caught.  

I'm sure that there are some sites out there with valid info, but I doubt that you can get access to them without being a licensed investigator, if then.

The best I've found.
http://www.pipl.com/

ETA: Disregard. Misread.