Well I cant speak for what goes on in the US, but over here in the UK the police do have and require full time Computer Forensics experts. However in that line of work for the police over 60% of your time will be spent on child porn cases. This kind of work is not for the faint hearted, and is something you should think long hard about if you wish to go into forensics. I know that I could not handle that kind of work.

SittingDuck