Diddy Defense Moves For Mistrial

Diddy's defense lawyer cried out for a mistrial Wednesday ... after a witness revealed fingerprints connected to the alleged break-in at Kid Cudi's Hollywood Hills house had been destroyed.

An arson investigator was testifying about the Molotov cocktail thrown into Kid Cudi's car back in January 2012 ... prosecutors believe the device was thrown at the behest of Diddy in a jealous rage over Cassie.

The arson investigator testified his unit had recovered DNA on the bottle used for the firebomb ... the partial DNA was from an unknown woman.

The investigator then testified Kid Cudi had given his unit fingerprint cards from a December 2011 burglary at his home ... a burglary at which Diddy was allegedly present.

Now the drama ... the investigator revealed those fingerprint cards Cudi had given them were destroyed in 2012 by the LAPD ... the defense jumped on this, claiming it could be exculpatory evidence if the fingerprints at the burglary didn't match the fingerprints at the arson scene.

The defense argued the prosecution knew the insinuation would prejudice the defense's case but proceeded anyway.

The jury was sent out of the courtroom and Diddy defense attorney Alexandra Shapiro said the feds were "trying to plant the idea with these jurors that Mr. Combs had something to do with the destruction of these fingerprints."