I’m not one either, but I would think unless you want to suggest the bullet was removed form the shootee and inserted into the late lamented Spaz, the only “broken” link in the chain of custody is the one between the gun from which it was fired and the aforementioned Spaz, and a good examination may fix that one.
The bullet could have come from another incident, if the contention that he got out of TwinPeaks without law enforcement attention is true.