Dr. Conrad Murray Manslaughter Trial -- The Defense Rests

The fat lady is about to sing in the Dr. Conrad Murray manslaughter trial -- because the defense has rested its case and are now gearing up for closing arguments.

Closing arguments are scheduled to begin Thursday morning -- but the defense won't be submitting any new evidence ... so if they haven't needled the jury with reasonable doubt yet in the death of Michael Jackson, they're facing an uphill battle.

It's also worth pointing out -- jurors notoriously hate coming back to court on Monday if they can help it ... which means there's a 99.9999% chance they'll come up with a verdict by Friday, presuming closing arguments don't drag on.

The prosecution rested its case over a week ago -- but while the case was impressive ... it wasn't 100% iron-clad.

So we gotta ask ...