As I mentioned a few posts back, tool marks from the instruments used by SP can be as good or better than a fingerprint. Burglars, like us, are habitual creatures. We like to do things that work for us over and over. Burglars generally have "kits" that are comprised of their preferred tools for B&E. Those tools have machine marks (much like the striations on the insides of gun barrels). Those machine marks leave impressions in whatever they strike. Whether a door, a window casing, the trunk of a car, the impressions are the same, because the tool used to make the marks is the same. Think of the study of those markings as a kind of "tool ballistics".
If I'm not mistaken, tool markings were very important in the case of Daniel Harold Rolling, known as The Gainesville Ripper. He was an American serial killer who murdered five students in Gainesville, Florida, over four days in late August 1990. His MO was using a screw driver to pry open sliding glass doors to gain entry. To my knowledge, he didn't leave fingerprints. As this was the period before DNA was an acceptable investigative tool, police relied on standard police investigative techniques. Tips from people who had known Rolling raised police suspicions and they began a search for him. As it turns out, he had been arrested on a shoplifting charge which gave the PD cause to search his woodland campsite. It was there that they found more incriminating evidence, including his burglary kit containing the screwdriver used to gain entry into the students' dorms. The tool marks from the doors matched tool marks reproduced by the tool itself. As good as a fingerprint. So there is another instance where toolmarks contributed to solving serial murders.
This case is baffling to a great degree, but not unsolvable as far as I can see. If SP left his tools behind and even if he didn't...well, the marks they left behind may well compare to marks left behind during less tragic prior break-ins, where cars were seen entering or leaving a crime scene or witnesses were able to provide, if only, hazy descriptions of the perp. The fabric of a case is comprised of many single threads of evidence woven sometimes painstakingly over a long period of time and a number of possibly linkable cases.
If you look a few posts back, you'll see my post about the crime statistics for Midlothian in 2016. The overwhelming number of those crimes were property crimes. Did SP break in elsewhere? Before or after this crime? Seems like there's a lot of B&E action going on...but only one murder. Missy's murder. It looks like SP added a gun to his burglary toolkit. That's called "escalation". A bad sign for Midlothian.
