Diddy‘s protection lawyer cried out for a mistrial Wednesday … after a witness revealed fingerprints related to an arson assault towards Child Cudi had been destroyed.

An arson investigator was testifying concerning the Molotov cocktail thrown into Child Cudi’s automotive again in January 2012 … prosecutors imagine the system was thrown on the behest of Diddy in a jealous rage over Cassie.

The arson investigator testified his unit had recovered fingerprints on the bottle used for the firebomb … the fingerprints had been from an unknown lady.

The investigator then testified Child Cudi had given his unit fingerprint playing cards from a December 2011 housebreaking at his house … a housebreaking at which Diddy was current.

Now the drama … the investigator revealed these fingerprint playing cards Cudi had given them had been destroyed in 2012 … the protection jumped on this, claiming it might be exculpatory proof if the fingerprints on the housebreaking did not match the fingerprints on the arson scene.

The protection argued the prosecution knew the insinuation would prejudice the protection’s case however proceeded anyway.