maybe i missed something but..
what exactly was the motive for killing the girls?
i saw this movie a couple times back in the 80's when it was on HBO and just recently watched it again on DVD (took long enough) and the motive wasn't clear to me then and still isn't now.
the only thing i can come up with is it had something to do with DM not wanting to pay royalties to the girls for the use of the their face and body in the computer generated ad's but that's a pretty weak reason for killing someone.