Collector Douglas Latchford, 86, and scholar Emma Bunker, 87, together wrote three books that are core reference works in the field of golden-age Khmer art and have been invaluable consultants to the national museum in Phnom Penh as it assembled a collection in the aftermath of Cambodia’s late-20th-century calamities. But a current criminal case suggests that the pair also spent decades providing false ownership histories for looted art.