AAIB YAK Screwdriver Accident Report - Questions

[zalt]

Sadly a fatal accident caused by a control jam due to a screw driver...

http://www.dft.gov.uk/stellent/groups/dft_avsafety/documents/page/dft_avsafety_024587.hcsp

Two questions jump out:

The first (and serious question):
"DNA testing however, showed that the pilot had come into contact with the screwdriver at some point prior to the accident"

Is this really possible? Can you match (say) a geasey hand mark? Is so why do the Police still use finger prints?

Secondly (and more retorically) on Safety Recommendation 2003-72:

"The CAA should publicise the circumstances of this accident in order to bring to the attention of Licenced Engineers (LAE) and maintenance organisations the need for them to have in place an effective tool system that reduces the likelihood of tools being left in aircraft after maintenance."

Does this mean the AAIB only think the CAA read their reports?

[ferrydude]

Interesting read, There was a description of a similar incident recently in a major aviation publication. Elevator jammed by vice grips, left in place by the author, an airline pilot and Yak owner. He actually left the vice grips while performing maintenance that he was not authorized to do, they later jammed the elevator almost causing loss of control. I wonder how many Mechanics/Engineers have been blamed for tools left in place or otherwise illegal maintenance performed by aircraft owner/operators?

[zalt]

In Stephen Barlay's 1960's book 'Aircrash Detective' there was a story of a court of inquiry into a Viscount accident that went awry when it was revealed that a screwdriver had been found in the wreckage. This then had then mysteriously gone missing only to be found being used elsewhere in the hanger.

In the end it was shown that this had not caused a jam, though as the AIB could not identify the actual cause of the accident (flying controls or otherwise), assorted lawyers had leaped on the screwdriver at the inquiry as the probable cause.

[Bus429]

This is a problem faced by many certifying engineers; he/she who signs last gets the blame.
In light aviation particularly, where there is an element of pilot maintenance (sometimes beyond the scope of their pilots' licences), the LAE is particulalry vulnerable.
Other engineers sometimes perform, usually minor, line maintenance without making a tech log entry, leaving the last certifier, in the event of a related incident, also vulnerable.