Just to reopen this.....
It was never a foot"print", it was more properly referred to as a foot"track".
A footprint would be collected forensically like a fingerprint, so that identifiable ridges and swirling patterns would be visible.
The foottrack was on a terry-towel-like serface, fuzzy and not nearly fine enough to capture a "print". One of the forensic folk commented that because of the receiving medium (the terry-towel mat) it was impossible to draw anything but the most general of conclusions. Indeed, because of the receiving medium, the measurements of the track could be off by a good measure.....
From the Massei report of 2010, Massei cites Professor Vinci, and then goes on to (wrongly) discount what he'd said...
Apparently, Vinci said that what was also key, was that one should never take just one sample of a foottrack while the subject is sitting or relaxing. It should be taken while the subject is walking, for these purposes along a long piece of paper to capture what the foot looks like in motion.
The long and the short of it was that Professor Vinci found that one of Raffaele's toes had been missing, if one assumed the bathmat track had been his. Why is a whole toe missing?
If you give a read to Massei's reasons for ultimately rejecting Professor Vinci's views, it is not really because any other expert had proven that that foottrack had been Raffaele's.
It was because Massei had been locked into assuming the track had to have resembled EITHER Raffaele's right foot OR Guede's right foot. Of those two, so said Massei, it more resembled Sollecito's.
Stellar reasoning. There had been actual proof that it had not been Raffaele's, but if forced to chose, Massei said it must have been Raffaele's. Not because the forensics proved it as such, but because once Guede had been eliminated (which he had not been), the only candidate left was Sollecito.
Even though the medium on which the sample had been collected could not support that view.
