/prosecution rests caseI appreciate the "devil's advocate" position.
So, this generation of GMC 2500 has drum rear parking brakes. They are inside the rotor. I guess drums can get heated up too, but I don't think the drums, not being used, would get as hot as the disks. Also, it was a basically flat course with only gentle slopes over long distances anywhere. The speed was under 6 mph with the entire route being 1.4 miles, beginning to end, unless something was seriously wrong with the brakes, I think you can drag your brakes for 1.4 miles at 3 to 6 mph and have little to no appreciable fade, at least they won't go completely away.
That generation truck did not have pushbutton start.
The transmission is shifted from the column shift with a cable. (6L90, not 4L80) Electronics are only used to shift between gears in drive. It can be shifted into park while moving. Granted, if you have enough momentum, the park pawl can be destroyed and you might keep rolling. A few guys stopped it with body weight eventually.
I am actually wondering if there was even a parking brake installed. I'm also wondering about something physically blocking the brake pedal from being depressed.
Oh, and the rusty brake line issue was solved for the GMT900 platform which this is. What I can't account for is a guy making up his own brake lines to account for a lift.