[md2576]

A smart criminal would have traveled to the rental agency close to an airport and placed a shell casing from thier gun into an unlocked truck they've never used to throw off the investigation.

[BiffSchneider]

It wouldn't throw it off that much, now would it? Presumably all the cops would have to do is interview the person(s) who rented the truck during the period. And interview the people at the rental agency.