Necrophilia has been documented in various lizard species, including  Ameiva ameiva, the leopard lizard, and Holbrookia maculata. There are two reports of necrophilic behaviour in the sleepy lizard (Tiliqua rugosa). In one, the partner of a male lizard got caught in fencing wire and died. The male continued to display courtship behaviour towards his partner two days after her death. This lizards necrophilia was believed to stem from its strong monogamous bond. In one study of black and white tegu lizards, two different males were observed attempting to court and copulate with a single female corpse on two consecutive days. On the first day, the corpse was freshly dead, but by the second day it was bloating and emitting a strong putrid odor. The researcher attributed the behaviour to sex pheromones still acting on the carcass.Male garter snakes often copulate with dead females. One case has been reported in the Bothrops jararaca snake with a dead South American rattlesnake. The prairie rattlesnake (Crotalus viridis) and Helicops carinicauda snake have both been seen attempting to mate with decapitated females, presumably attracted by still-active sex pheromones. Male crayfish sometimes copulate with dead crayfish of either sex, and in one observation with a dead crayfish of a different species.In anurans, it has been observed in the foothill yellow-legged frog, the yellow fire-bellied toad, the common frog, the Oregon spotted frog, the common Asian Toad, Dendropsophus columbianus, and Rhinella jimi.
When his attempts failed, and his male victim died, he would keep the corpse until it decomposed beyond recognition,  masturbating and performing sexual intercourse on the body. He would perform sexual activities before and after murdering his victims. Dahmer explained that he only killed his victims because he did not want them to leave. More modern necrophiliacs include Scottish serial killer Dennis Nilsen, and English David Fuller, who is considered the worst offender of this kind in English legal history.Havelock Ellis, in his 1903 volume of Studies of the Psychology of Sex, believed that necrophilia was related to algolagnia, in that both involve the transformation of a supposed negative emotion, such as anger, fear, disgust, or grief, into sexual desire. Classification
In the Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5), recurrent, intense sexual interest in corpses can be diagnosed under Other Specified Paraphilic Disorder (necrophilia) when it causes marked distress or impairment in important areas of functioning.Forensic Psychologist Anil Aggrawal introduced a ten tier classification of necrophiliacs based on increasing severity of disorder. Additionally, criminologist Lee Mellors typology of homicidal necrophiliacs consists of eight categories (A–H) and is based on the combination of two behavioural axes: destructive (offender mutilates the corpse for sexual reasons) – preservative (offender does not), and cold (offender used the corpse sexually two hours or more after death) – warm (offender used the corpse sexually less than two hours after death). This renders four categories (A-D) to which Mellor adds an additional four (E-H):

Category A (cold/destructive), e.g.