Classify the relation of question with context to one of these categories: 1) award received, 2) based on, collection, 3) conflict, 4) constellation, 5) convicted of, 6) date of death, 7) director, 8) drafted by, 9) educated at, 10) medical condition, 11) military branch, 12) narrative location, 13) occupation, 14) original network, 15) parent company, 16) point in time, 17) production company, 18) residence, 19) series, 20) service entry, 21) sex or gender, 22) spouse, 23) standards body question.

Context : John David Duty (April 25, 1952 -- December 16, 2010) was an American who was executed in Oklahoma for first-degree murder. 
Question : For what crime was John David Duty prosecuted?
convicted of

Context : The Madonna Litta is a late 15th-century painting, traditionally attributed to Leonardo da Vinci, in the Hermitage Museum, Saint Petersburg. 
Question : What is the name of the place where Madonna Litta can be found?
collection

Context : China Airlines Flight 642 was a flight that crashed at Hong Kong International Airport on 22 August 1999. 
Question : The date of China Airlines Flight 642 was what?

point in time