[Grendel]

I don't use it but your application of forensic courtroom diagrams/scenes could be filled by Poser or DazStudio very well if you're familiar with them. You could use your sketchup models of environments to build your 'set' and then import it into Poser or DazStudio and populate the rest with pre-made content(including human models/victims) for very little effort.

This type of workflow lends itself to walk-thru's and demonstration/exhibit quite well.

If you want to go the route of making everything yourself until you become proficient at modeling you could have problems with deadlines.