It is most certainly not any LAME's responsibility, any more than the a LAME is responsible for the airworthiness of the aircraft -- that is the responsibility of the registered operator, who is also responsible for all required maintenance being carried out -- not the LAME who certifies return to service.
False dichotomy.
When the registered operator pays a LAME to perform an inspection on an aircraft, and the LAME takes the money and certifies for the completion of the inspection, the LAME is under numerous contractual, common law and legislative duties in relation to the airworthiness of that aircraft.
I'd urge all LAMEs to be
very careful in relying on what Leaddie suggested.