For an idea for a Sleuth Expansion I have done some research on evidence that could be left at the scene of the crime. First off what are your thoughts about pixel hunting to collect the actual evidence itself? And here's more evidence that could be used in the game.
Using your smart skills you could narrow the fingerprint down to a whorl, right loop, left loop, arch, and tented arch.
Combined with the rh Blood system there are 8 different Blood types you could narrow the blood left at a Crime Scene to. A+ A- B+ B- O+ O- AB+ AB- The suspects blood types should reflect how common the Blood types are so most of your suspects should have A+ and O+ Blood types. And since only .07% of people have an AB- negative blood type AB- negative blood left at the crime scene would be your Three Legged Tom.
Since you wont be able to tell a suspect blood type of fingerprint type from an initial interview you may have to use your Research Skill or Locking Pick skill to take a hairbrush with a suspects hair and fingerprints on it to figure that out. In saying that maybe this should be secondary evidence a killer leaves at the scene of the crime since you may not have those skills. IE (Killer leaves one of Hair, Handwriting, Thread, and Footprint) and one of ( Blood and Fingerprint Evidence)