Phenomena such as fantasy, anger and temptation can be studied in a non-forensic population and insights tentatively extrapolated to lust killers. Consider the fantasy experienced by someone addicted to drugs. An image of a drug might pop into the conscious mind and if it will soon become available, the imagery can be pleasant. Otherwise, it can be tormenting. Fantasy features large in lust killing and appears to play a causal role. If a person already has a tendency towards sexual violence, watching pornography can increase this. The cold-to-hot empathy gap refers to the difficulty someone in a cold state has in appreciating the temptation of being in a hot state. The term ‘displaced aggression’ refers to aggression arising initially from a situation where retaliation against the trigger would be difficult. Sadism can be studied in non-forensic samples. A number of psychoactive drugs can increase the tendency towards aggression.