this mission tells you how
basically you search by name
BK1 Search And Delete (available after "Rigged to Blow")
Go to Brucie's garage. Brucie wants you to take out someone who is
"******* with him". You need to get into police files to find the
guys whereabouts. Steal a cop car. It's easiest to do this by going
to the neariest cop shop and pinching a car from out front. The other
way is to dial 911, wait for the plod to show. When the cop gets out
get in that car on the passenger side and drive off quickly. Lose your
wanted level, pack the and access the police computer. Search for
"Lyle Rivas". You'll find him in Rotterdam Avenue. Go there and enter
here's a video
http://www.youtube.com/watch?v=-ZP-6Ey11vo
if you like cheats
http://www.gamefaqs.com/pc/952150-grand-theft-auto-iv/cheats