Walt & Jesse are forced to destroy their RV when a break in Hank Schrader's "Blue Sky" meth case leads him to Jesse. Given his conversation with Hank, it can be believed that Old Joe has a fairly extensive legal knowledge. Not only does he hold his ground against Hank, he also helps to delay his search by making him get a warrant. When Hank is led away by a phony phone call by Saul Goodman, Old Joe destroys the RV. ("Sunset")
Walt, Jesse, and Mike Ehrmantraut visited Old Joe to borrow a giant magnet from his junkyard to destroy Gustavo Fring's laptop inside the police evidence locker. He sells them the magnet, 42 car batteries and an old truck to transport the magnet. ("Live Free or Die")
Joe builds some of the equipment for Walt and Jesse's new portable lab. ("Hazard Pay")
Walt and Todd Alquist mentioned Joe later while disposing of Mike Ehrmantraut's body after Walt killed him. Todd says he delivered Mike's car to Joe to perform an "RV job" and Joe got it.("Gliding Over All")
- Joe is well educated in law. He used his knowledge against Hank when defending Walt and Jesse ("Sunset").
- He also appears to have a working knowledge of engineering, as he is able to set-up the large electromagnet that Walt, Jesse and Mike use to erase Gus' computer from outside the DEA storage vault ("Live Free or Die").