How does Greenspan know what TPS did? Do you not think that police officers and the private investigators ever talk? Of course they do, they are former coworkers, and they compare notes, I am quite sure. So I think Greenspan knows generally what LE did at the scene, based on what the private investigators were told by their friends still in the police force.
I think Greenspan also knows at least some of what LE
didn't do at the scene, based on whatever evidence the private investigators found once they were given access to the house. For instance, if hair or fiber evidence remained at the scene, it's because LE didn't collect it. For instance, he states that among other clues, LE missed over 25 fingerprints at the crime scene.
Fingerprints, DNA not identified 10 months after Sherman murders: lawyer | Watch News Videos Online
In the case of the door locks, lab analysis can determine if the locks were picked based on marking and scratches on the lock components. If the private investigators got to the house and found that the locks had not been removed for lab and scientific analysis, then they can reasonably conclude that LE did not adequately perform scientific analysis on the locks to determine if they had been picked. Here is his quote on the matter (RBBM):
"...
A thorough investigation of all points of entry into the home was not done or had missed a potentially key piece of information that could have helped police more quickly focus their investigation: a lock that may have been tampered with or forced"...
I know you don't believe Greenspan, I accept that. But I see no logical reason for him to be complicit in such a coverup, and to lie about evidence that the private investigators say they found at the scene (
which by the way was subsequently turned over to LE for analysis and investigation).