Table 2 shows the cases by crime category, in which 51 (43%) of the victims were male and 67 (57%) female. The average age of the victim was 37, and the average age of the offender was 36.
Table 3 below shows that the types of offences varied greatly between the male and female victims. As a consequence, for women, the rate of death per attacks was 1 in 6 but for men it was 1 in 25. While some of this may be explained by the fact that men are on average stronger and larger than women, there is also research which shows that men are more likely to use a gun or a knife (Brown 1987).
In 51 (43%) cases, the relationship was recorded as spouse or cohabitee (or ex); in 52 (44%) cases, as lover, boyfriend or girlfriend (or ex); in 13 (11%) cases, as parent or family; and in two (2%) cases, as civil partner (or ex).
Table 4 shows that there was prior recorded contact with police for 53 (45%) cases and there was little difference between male and female victims, 46% and 42%, respectively. In 16 of the 53 cases (30%), the most recent previous contact was a non-crime domestic incident, and of the remaining cases, 16 were actual bodily harm (30%). In 87% of the cases, the previous offences were committed by the same offender.
Table 5 shows that where there had been prior contact, nearly half of the cases involved only one prior contact for a domestic incident with the police. Overall, 76% of the sample had only one or no prior contact with police prior to the deadly violence.
Table 6 shows that the risk assessments for 21 cases (40%) with prior police contact had been classified by the responding officer as standard risk, 21 (40%) assessed as medium risk, five as high risk (9%) and there are six cases (11%) where the assessment is unknown. Only one of the 13 murders had been assessed as medium risk with the remaining assessed as standard risk. Not one of the murder cases with prior contact had been assessed as high risk. In respect of seven other murders, there was no prior contact. This initial analysis suggests a high number of false negatives for the risk assessment tool as it was applied in Thames Valley. In respect of murder, the false negative rate is 100%, and in the case of non-deadly assault, the false negative rate is 87%. The combined false negative rate is 90%.
A neighbouring police force (Hampshire Constabulary) provided its own data on prior police contact with cases later developing into deadly violence, using exactly the same offence definitions. No prior contact was found to have been 48% in Hampshire compared with 55% in Thames Valley.
Case Control Samples: Males
Table 7 shows the comparisons between the male offenders in the domestic murders and serious assaults studied and the 150 males in the case control sample drawn from the broader population of those arrested for violence. There are some striking similarities between the groups but also some differences.
There are few differences of any magnitude in Table 7, but these are of great interest. One falsifies the commonly held view is that the most serious domestic assaults are a result of escalating harm and violence. In sharp contrast to the escalation claim, the evidence shows that offenders in the case control have significantly more arrests and convictions for violence than the offenders who committed domestic murder and serious assault. This evidence contradicts the hypothesis upon which much of the risk assessment tools are based.
The average age of first criminal justice contacts with the male deadly violence offenders is somewhat older than for the case control males. The average age at first arrest for violence is significantly higher in the cases than in the control sample, t (98.51) = −3.13, p = 0.002, d = 0.35. Also the average age at first conviction is significantly higher in the cases than in the control sample, t (83.47) = −2.19, p = 0.03, d = 0.48. Lastly, the age at first conviction for violence is significantly higher in the deadly assault cases than in the control sample, t (78.90) = −3.18, p = 0.002, d = 0.54. All three have a small to medium effect size.
These three comparisons show that the average age of onset of criminal career is later for those offenders who commit serious domestic assault than for those who commit all violence. Again, the evidence does not support the commonly held view that serious domestic assaults result from escalation over the years but suggest that these attacks are often much less predictable and perpetrated by those with less of a criminal history and a criminal history with a much later onset. In the cases with no prior violence, the serious assault came “out of the blue”.
In respect of the warning marks on PNC there are some differences between the two groups. In respect of most categories, the offenders in the Thames Valley deadly violence cases were more likely to have the warning marker than the case control. Thirty-three percent had a warning marker for weapons compared with 23% in the case control sample. Six percent had a warning marker for firearms compared with 4% in the case control sample. There were smaller differences in respect of markers for drugs, and the levels of employment varied slightly. However, the largest relative risk ratio is found with the PNC suicide marker, which was collected some years after the act of deadly violence. While it is not possible to separate suicide markers in these data entered on PNC after the deadly violence from those entered before, the indication of high prevalence of mental health issues seems worthy of substantial further research. This finding on the prevalence of mental health issues also replicates the review in South Wales Police (Robinson 2006).
Table 8 shows the comparisons between the female offenders in the domestic deadly violence cases and the case control sample drawn from the broader population of females arrested for violence. In none of the cases was the difference significant and the effect sizes were small or less than small, with the exception of PNC warning for weapons. While this difference was not significant due to small sample size, the prevalence of PNC warning for weapons among the female serious assault offenders was substantial. Almost one third of these offenders had a PNC weapons warning, compared to 7% for controls. The effect size is well beyond large. The relative risk ratio is 4.75 meaning that offenders who are known to have used weapons are nearly five times more likely to commit domestic murder and serious assault than those who do not.