Joey Garbaldi was a mafia lieutenant.
Throughout The Series[]
In the Season Three episode 9 Days, Jake Peralta brings up a cold case from his first year as a detective. The main perpetrator is Joey Garibaldi, who evaded Jake 8 years before. He and Holt worked the case while quarantined due to the infectious disease, Mumps, which they contracted from their first lead, Nick DiTullio.
Amy came across a recipe for baked ziti in the case files that were strewn across Captain Holt's house and made it for Jake and Holt. This led them to realize the recipe wasn't a recipe and was in fact a code for Garibaldi's phone number.