I’m still not convinced that Triggs actually was riding on the sidewalk.

Apparently there was one eyewitness who thought he saw Triggs riding on the sidewalk. But eyewitnesses remember seeing all sorts of crazy stuff all the time.

There are other witnesses who saw Triggs bicycling through that intersection on a regular basis and never using the sidewalk.

The scenario that killed Trigg is almost certainly that outlined here:

http://mobikefed.org/2006/08/bicyclists-how-to-avoid-being-hit-by.php

This problem (large trucks swing left in preparation for a right turn, making it look as though they are starting a left turn rather than a right turn) would have been exacerbated if the driver didn’t signal or the signals were malfunctioning–as was reported by other witnesses.