Former MI6 agent James Gustaf Edward Le Mesurier died as a result of falling, according to the forensics report.
Mesurier, 48, was found dead in Istanbul’s Beyoğlu district early on Nov. 11 and an investigation was launched into the incident.
Blood and tissue samples were examined, and only sleep-aids were found in Le Mesurier's blood, Turkey's state-owned broadcaster TRT reported, adding that no foreign DNA was found on the tissue.
Le Mesurier was the director of Mayday Rescue charity that trained members of the volunteer rescue workers' group Syria Civil Defense, nicknamed the White Helmets.
Turkish authorities had placed a travel ban on Le Mesurier's wife.