The aircraft John bought second-hand, originating with builder Adrian Davis, was the only amateur constructed Long-EZ with a non-standard placement of the fuel tank select-handle, behind the left shoulder. The aircraft design plans called for placement on the console between the pilots knees. John also failed to conduct a proper pre-flight inspect of an unfamiliar aircraft, and departed the airfield drawing upon a nearly empty fuel tank.
https://www.ntsb.gov/news/press-releases/Pages/NTSB_Determines_John_Denvers_Crash_Caused_by_Poor_Placement_of_Fuel_Selector_Handle_Diverting_His_Attention_During_Flight.aspx
Here’s another fatal crash that involved the fuel selector.
https://aviation-safety.net/wikibase/wiki.php?id=40973