Homicide is often made more likely by 'enhancers' such as drugs, alcohol, mental health or the involvement of street gangs. This thread summarises what we know about factors that make homicide more likely. 🧵

DRUGS AND ALCOHOL Homicides very often involve drugs or alcohol: in 64% of all homicides, either the victim and/or a suspect was believed to be under the influence of alcohol or an illicit drug at the time.

About a quarter of suspects had been drinking at the time they killed the victim and 18% of suspects had taken an illicit drug, while 11% were under the influence of both drugs *and* alcohol when they killed someone.

Suspects were particularly likely to have been drinking in homicides related to fights, brawls, etc. (33% of suspects had been drinking) and in domestic homicides (32%). Suspects were most likely to be under the influence of drugs in homicides involving an irrational act (35%).

Similarly, over a quarter of homicide victims had been drinking when they were killed and about 15% had taken an illicit drug at the time they were killed, while 8% were under the influence of both drugs and alcohol when they were killed.

Victims were particularly likely to have been drinking at the time of their death in homicides related to fights, brawls, etc. (42% of victims had been drinking), and to have been under the influence of drugs in homicides driven by the suspect committing a reckless act (34%).

Even if they weren't under the influence at the time they were killed, drug users were at higher risk of homicide: 34% of homicide victims were believed to be drug users, much more than the 10% of adults who say they've used an illicit drug in the past year.

Homicide suspects were even more likely to be drug users: 48% of suspects were known to use illegal drugs, including 38% of suspects who were *not* believed to be under the influence of drugs at the time of the homicide.

People believed by police to be drug dealers were also at much greater risk of being killed in a homicide, especially in some circumstances: 54% of all people killed during robberies were believed to be drug dealers, along with 43% of people killed in long-running feuds.

MENTAL HEALTH Police believed about 17% of homicides to be linked to a suspect's mental health. Overall this was similar whether the victim was male or female, but homicides of women by men were more likely to be linked to the suspect's mental health.

Suspect mental health was particularly likely to be a factor in homicides relating to domestic abuse or in which the suspect committed an irrational act, but only very rarely a factor in homicides related to the suspect committing another crime, a reckless act, or child abuse.

Homicides were also more likely to be linked to suspect mental health if they were also linked to drugs: mental health was a factor in 25% of homicides where the suspect had taken an illicit drugs, compared to 15% where they had not.

GANG HOMICIDE About 58 homicides each year (about 10% of all homicides) were believed to be gang related. Gang-related homicides are less common than many other types of homicide. For example, 26% of homicides (120 each year) met the definition of domestic abuse.

Gang-related homicides were heavily concentrated among young victims: 34% of homicides of victims aged 10–19 were gang-related, along with 22% of homicides of victims aged 20–29. But for victims aged 30 or older, only 3% of homicides were gang related.

Victims of gang-related homicides were almost exclusively male: 14% of all homicides of male victims were gang-related, compared to 0.3% of female victims (there was only one gang-related homicide of a female victim in the data we studied).

Black victims were also more likely to be killed in gang-related homicide: 36% of homicides of Black victims (and 11% of homicides of Asian victims) were gang-related, compared to 5% of homicides of White victims.

Combining data on age, sex and ethnicity shows huge variation in the risk of being a victim of gang-related homicide: Black men aged 20–29 were 49 times more likely to be the victim of a gang-related homicide than White men of the same age.

Gang-related homicide offenders were much more likely to be young: 90% of gang-related offenders were 29 or younger, compared to 51% of offenders in non-gang-related homicides. Gang-related homicide offenders were also more likely to be Black and less likely to be White.

Gang-related homicides are often linked to on-going disputes, happen during feuds or brawls, or are committed in the course of the offender committing another crime.

This analysis of homicide enhancers in England and Wales comes from a report written by me and @iainbrennan.bsky.social for the UK College of Policing. You can get more detail at lesscrime.info/post/homicid... HT to @jerryratcliffe.net for the concept of crime enhancers.