Is AD compliance ever physically verified when maintaining an aircraft? As we all know around here, national aviation authorities put out Airworthiness Directives mandating certain changes be made to aircraft during their service life so that the aircraft can stay airworthy.  The paperwork for these ADs is part of the aircraft logs, and thus stays with the aircraft for the life of the aircraft.

However, just because an AD is marked as complete and closed out in the paperwork does not necessarily mean it has actually been completed.  This was a causative factor in the Omega flight 70 mishap, where an engine fell off a 707 shortly after rotation and damaged the plane to the point where it could not climb out.  The investigation revealed that although the applicable ADs were marked complete, the upgraded part required to be installed to close the ADs out had not been installed on the mishap aircraft.  Instead, a prior owner had marked the AD at the time complete when it had not actually been fully closed out.

How can an aircraft owner ensure that the ADs that the paperwork says have been closed out on an aircraft have actually been closed out and not simply pencil-whipped?  Are such verifications ever performed during maintenance or inspections (including pre-/post-sale inspection), or is the paperwork trusted absolutely?  Furthermore, how can an inspecting mechanic accurately determine the completion status of ADs?  (For the 707 AD in question in the Omega 70 mishap, this could be done with a small template and some mechanic time inside the pylon, but I suspect some ADs aren't that easy...)
I can only speak for commercial aviation, but in my experience, we generally have 100% RII buyback on initial AD compliance issues. For example, if we have to run a new wire bundle or reroute a wire bundle as part of an AD, it has to be "bought off" by either a QC inspector or an RII-qualified mechanic. In these situations, I would say that the work is done properly 99% of the time. Rarely would someone put their name on something that's done incorrectly if they don't have to go back and do the work themselves. The response is generally "Call me when you get it right." 

Where I think the FAA severely lacks oversight, in my opinion, is future compliance in upholding the standards of the AD. On the initial AD, you're not allowed to deviate one iota from the original without a very special process put in place. But what happens when you deviate 10, 15, or 20 years down the road?

Hypothetical scenario: An AD is written to reroute a wire bundle from other wire bundles because of some safety issue. The AD is complied with and life goes on. Twenty years later, a mechanic disassembles all the wiring in the area for "X" maintenance issue. He turns it over to the next shift to reassemble it. Next shift has no idea how it goes back together. It's not marked as AD wiring. There are no instructions on how it all goes back together (save for the AD paperwork from 20 years ago), so the mechanics put it back together per the standard wiring practices manual. They bundle and clamp. Bundle and clamp. They do a beautiful job, but guess what? It violates the purpose of the AD from 20 years prior. Do you think the FAA follows up on that? Nope. The company? Nah. They have paperwork showing the AD is complied with. So it's up to each mechanic to determine if what they're working on is part of an AD (even one from 20 years ago), despite no special labeling or instructions, and maintain that AD compliance. As we mechanics joke, "It'll all come out in the investigation." 

My experience is that as time goes by, the integrity of many AD's slowly dissolves. That being said, if we as A&amp;P's even smell the faintest whiff of an AD, our antennae perk up and we are very careful to maintain that compliance. AD  violations are the surest way to get a nice letter in the mail from Mr. FAA.