Green’s Dictionary of Slang

(US Und.) an incompetent lawyer who is given clients by court or jail officials; he has no substantial legal knowledge, charges minimal fees, and usu. loses.

1976

Sutton & Linn Where The Money Was (2004) 392: The ‘dirty shirts’ – the ambulance chasers of the courtroom [...] They wouldn’t know how to actually try a case if their life depended on it.