Source: Rechtsmedizin, Burkhard Madea Hrsg. (German Forensic Medicine Textbook by Burkhard Madea MD). Germany. Case from 2004.
Auto-translated. 24 year old man had intentionally caused the death of his 28 year old domineering gay partner. During the strangulation fetish session he was acting as a safe spotter. But was on purpose strongly encouraging the 28 year old to push it further and further, while hand “stimulating” his partner's penis so he would not want to stop. And when finally his partner went too far and had passed out, he just stood and watched him getting strangled to death. And immediately right after that calling police to report accidental death and that he had found him like that when he came to his home.
But police got suspicious. And upon further interrogation the 24 year old had finally admitted of planning death of his gay lover. As a self-defense against his partner sexually using him for months in very domineering degrading rough way, like a s-ex toy slave. With his hands being tied behind his back on many occasions. And blackmailing him by threatening to reveal certain legal issues from the 24 year old's past to his government job employer, if he dared to leave him.
On scene photos the deceased can be seen as he was found (right after the paramedics had taken away the life detecting heartbeat sensors from his chest). Sitting with his buttocks on a slightly extended part of the ottoman cube and with a belt holding him by the neck, zip tied to the leg of an overturned coffee table from above him. Thus keeping the corpse in the same position as when he got strangled. Mirror was placed in front of him, so he could to look at himself during the process and see his partner hand “stimulating” him. There were dripping traces of his dried sperm on the mirror. Indicating ejaculation before passing out. A metal kitchen tray was under him, so his sperm would not get on the carpet. Corpse’s penis also kept some of its erect status. A condition known as "rigor erectus"/death erection.
Corpse’s pushed out tongue also indicates that it was a very slow strangulation death, while the victim was in the passed out state. Taking almost 10 minutes for his heartbeat to stop beating (since it was rather a strangulation, with body in sitting down position, as oppose to full body suspension hanging death). His partner was regularly checking the victim’s pulse and calling the emergency services only after he did not detect any heartbeat. Which he had testified as taking almost 10 minutes of wait time.