OK, you've already got a ton of evidence to analyze! Neato.

bullets - 44 cal 35 yr old
tire iron - Garvey's blood
gun - Garvey's, not fired recently
paper - Tropicana Ave Car on roadside needs asst
ID - forgery
car seat - blood - "pig blood"
thread - cotton
pavement stain - more pig blood

print search on gun - were Garvey's.

search on ID - a copy that was killed exact same way 35 years ago. In that one, gun was found under car.

Hmmmm, I didn't see a gun under the car, did you? Head back to the crime scene and sure enough, there it is. Grab it with the gloves and bring it back to the lab.

It matches up, this is the murder weapon. Right at this point, you're told to go use the computer to watch a chat room. You see a quick sequence:
What's exciting?
Sutherland - cop killing. Aiboy went to see.
That was you?
Sutherland - drive out for yourself and see. It may remind you of another famous case.

This is crimechat.com. The cops say this is owned by Jack Riley, who lives near the scene of the crime. Time to go talk with Jack Riley.

CSI Crime scene Investigation Walkthrough