NAIROBI - A world-renowned ivory investigator whose detailed reports contributed to the fight against elephant poaching and the illegal wildlife trade, was killed at his home in Kenya, police said Monday. Esmond Martin, 75, died after being stabbed at his house in the Nairobi suburb of Langata on Sunday afternoon. “He was found dead in his house and had stab wounds,” said a police officer. “An investigation has been launched.” Martin, an American who lived in Kenya for decades, focussed on the demand end of the illegal ivory supply chain, describing, quantifying and analysing the Asian ivory markets in China, Hong Kong, Vietnam, Laos and elsewhere.