This is a very, very good post. If we want to brainstorm - what type of evidence found at the scene of a crime would be useful to a 1960s detective?
- a wallet
- clothes with some identifying mark (tshirt from a local company, etc)
- shoe prints
- fingerprints
- a weapon
- a signature tying the killer to previous crimes
What else? There’s a lot of possibilities here.
I'm going to brainstorm a little bit outside the box, but what if there were many items of evidence (disposable drinking glasses or beer or liquor bottles, discarded food containers, crack or meth pipes or lighters, cigarette butts, gloves) collected from the crime scene which would
normally be expected to implicate certain individuals (say ex-convicts who had DNA on file), but those individuals were reliably ruled out as involved because they had rock-solid alibis for the relevant timeframe? So, of many items of evidence collected when processing the scene, only a very small list of those items was ultimately determined by LE to be potentially reliable and they contain DNA which is not on file.
This could happen if:
(1) these individuals who were investigated and ruled out had at one time been homeless and used as "camp" the general area where the girls' bodies were found, leaving personally used items behind.
(2) the perpetrator gathered items from other locations (such as rehab facilities or job sites or parties) which he knew would implicate others who had DNA on file and purposely left these items at the scene of the crime to implicate those people.
Who might take advantage of such misleading evidence:
For (1):
A killer who himself might have been occasionally homeless and who camped at some point in the broader surrounding area (such as under the trestle bridge or somewhere at some distance across Deer Creek) or worked somewhere close by, but who attacked and killed where he knew others whose DNA was likely on file had camped and left many items behind. This could be a technique a person who spent some time in prison might have learned from other inmates.
For (2):
Someone who operated or attended a court-ordered rehab facility, where ex-convicts or others with DNA on file participated, and where he gathered items used by others there.
Someone who regularly employed as laborers individuals through the work programs associated with such facilities, knowing they were ex-convicts or others who had DNA on file, while he did not.
Either circumstance would require some planning, either to wait for the opportunity to commit these crimes at that particular location OR to gather the evidence in advance with a plan to plant it at the time of the crime or in advance of it.