frankie the snitch?

Frank "Lefty" "The Snitch" Rosenthal? From the Las Vegas Review Journal:

'Lefty' Rosenthal was an FBI snitch
by JANE ANN MORRISON

Back before he was mayor of Las Vegas, when he was the city's leading mob attorney, Oscar Goodman insisted he didn't represent snitches.

He represented Frank Rosenthal. Now that Rosenthal is dead, three former law enforcement sources with first-hand knowledge confirmed what was long suspected. Lefty Rosenthal was an FBI informant, whether his attorney knew it or not.

While Rosenthal was alive, no one would confirm it. Nobody wanted to be the one who got Lefty whacked. Read more.