'Jerry Springer' Producer -- Cops Say She Lied Over Sister's 'Suicide'

The 'Jerry Springer' producer whose sister died in their garage is now in the hot seat with the LAPD, because TMZ has learned cops believe her story about the death doesn't make sense.

Jill Blackstone's sister Wendy died in March from a combination of carbon monoxide poisoning and Xanax. At the time it appeared Wendy, who was blind and partially deaf, committed suicide ... even leaving a note.

Jill had said she had no idea Wendy wanted to kill herself. As for how a Weber grill and charcoal got into the garage, Jill told police the Weber grill was for warmth and the coals in the trash can were for roasting marshmallows.

But we've learned cops now paint a very different picture of what they say happened. Our law enforcement sources tell us when they first interviewed Jill she told cops she had no idea her sister wanted to kill herself. But cops say it's very clear Jill -- not Wendy -- wrote the "suicide" note.

Our sources say cops are "confident" Jill assisted her sister -- not out of vengeance but mercy for her condition. Even if Jill's motive was mercy-based, it would still be a crime, and we're told the case is now "on the front burner" for possible criminal prosecution.