DM's fingerprints, no MS fingerprints, on the steering wheel of TB's truck would be my first guess.
I would find it odd if a murderer went through the trouble of removing the seats from a vehicle where a murder took place, but could not be bothered to wipe off his fingerprints from the most obvious of places. That would seem to me to be another case of only doing half the job of covering your tracks, (and in this case, the far more difficult half) which would make me question whose tracks are really being covered and why everything not covered seems to point another person with no motive who will say nothing except that he is innocent.
Misdirection would be very useful to additionally cover your tracks should you violently murder someone. If you are worried that when you commit a crime that the police might eventually be lead to you through some clue you missed, wouldn't it be useful to leave misleading evidence pointing directly at someone else. Then, even if you ever were suspected and went to trial, you would have a built in defence, the misleading evidence would be there to automatically create doubt.