Developmental and Criminal Trajectories of Sexual Killing

Transcription

1 Developmental and Criminal Trajectories of Sexual Killing Ewa Stefanska, Foren.Psy.D

2 Objectives What is meant by the term sexual murder, and is the generally accepted definition too broad? Who is the true sexual murderer? Should sexual murder be conceptualised within a continuum of sexual aggression, or is it a unique type of offending? What are the factors that predict fatal and non-fatal sexual aggression?

3 Sexual murder in England & Wales Homicide perpetrators N = 6320 classified having sexual element N = 840 June 2012 estimates (NOMS; Stefanska et al., 2016) an increase from an earlier estimate by Beech et al. (2005)

4 Is sexual murder a discrete type of sexual offence? Sexual murderers are not qualitatively different from sexual aggressors (Stefanska, Beech, & Carter, 2016) But... There is a subgroup of sexual murderers who appear to represent a unique type of offender with lethal intent demonstrated in their offending (Healey et al., 2016) Between group differences do predict escalation from sexual aggression to murder (Nicole & Proulx, 2007) e.g. inappropriate childhood & adolescent behaviour

5 Sexual killers not all the same Ø Sadistically motivated - killing forms part of sexual fantasy (killing and sexual element closely bound) Ø Sexually motivated - killing is instrumental Part of decision-making process situational factors: e.g. victim resistance, use of alcohol, elimination of a witness (killing not a source of sexual stimulation)

6 Anger as a motivator? Ø At a physiological level erection and anger are regulated by the same brain structures (Myers et al., 2006) Erection a series of events between exciting and inhibiting forces of the ANS Norepinephrine needs to be inhibited Ø Anger induces release of norepinephrine (Bozman & Beck, 1991; Beck & Bozman,1995; Myers et al., 2006) 1) Sexual arousal and anger are negatively related

7 Anger as a motivator? Ø Sexual aggression exists - pathological functioning? (Myers et al., 2006) 2) Anger as a motivation does not explain the relation between sexual element and killing physical violence occurring subsequent to sexual act or sexual act following physical violence (Cusson & Proulx, 2007; Stefanska et al., 2015). Ø Considering the sexual element when classifying sexual killers (Carter & Hollin, 2014)

8 Time of death Sexual violence Perkins, D. (ATSA, 2017)

9 Current dataset (N= 350) Inclusion criteria Sexual murder (NOMS): Sexual element and/or sexual motivation was evidenced, suspected or admitted Non-serial: One or two victims, no cool off (Proulx, Cusson, & Beauregard, 2007) Female victims age 14 or older (Carter & Hollin, 2010) Data Public Protection Unit Database: Trial reports, social enquiry, psychiatric/psychological assessments, criminal records

10 Approach 1 Higgs, Stefanska, Carter, & Browne, 2017 Higgs & Stefanska, in press

11 Developmental and criminal histories of sexual aggressors Post mortem sexual interference proxy for those sexual murderers for whom there is a direct link between killing and sexual arousal Sexual aggressors: Life or indeterminate sentence for rape N = 253 sexual murderers sexual aggressors n = 72 Post Mortem Sexual Interference n = 89 No Post Mortem Sexual Interference n = 92

12 PMSI Time of death Sexual violence Perkins, D. (ATSA, 2017)

13 Sample of variables

14 Scale variables

15 Criminal history variables

16 Multinomial regression: Final model

17 Key features of PMSI sexual murderers Early social inadequacy (e.g. isolation, cruelty to animals, selfharm, violence to others) Adulthood social and sexual isolation Sexual deviancy (sadism) Low frequency of violent and sexual crimes

18 Key features of non-homicide sexual aggressors Lifelong anti-sociality Adulthood sexual promiscuity High frequency of all types of crime (sexual, violent, property etc.)

19 Multitrajectory model with fatal and nonfatal outcomes

20 Approach 2 Stefanska, Higgs, Carter, & Beech, 2017 Stefanska, Higgs, Carter, & Beech, 2018 Stefanska & Higgs & in press

21 Aim ØTo assign cases as belonging to indirect or direct group based on definitions by Carter and Hollin (2014) Evidence accepted by the court at trial N = 350 Direct SK n =174 Indirect SK n = 176 Decision not reached n = 89

22 Ø Indirect: Victim killed in order to eliminate witness Victim killed trying to escape sexual assault No sexual violence but killing occurred in a sexual context Ø Direct: Act of killing was sexually gratifying The purpose was to enable sexual acts with victim s body NOTE: both homicidal and opportunistic necrophiles included (Aggrawal, 2009) Ø Decision about the group could not be reached : Hypothesis about indirect and direct link valid (N= 350; 176 vs 174)

23 Direct SK Time of death Indirect SK Sexual violence Perkins, D. (ATSA, 2017)

24 Question 1. Are there any specific situational and MO factors that can predict the membership of the indirect and the direct group Predictor B S.E. Wald Sig. Exp(B) Secluded place Encounter different Stranger Victim target Weapon taken to scene Sexually frustrated Crime phase anger Pornography use Use of restrains Interrupted Vaginal penetration Anal penetration Biting Victim died of beating Unusual crime scene acts SeSaS score Constant Table 1: Logistic regression of situational and MO factors for indirect and direct cases

25 Test of Q1: Discussion of the results Ø Encounter at different place: two scenarios - victim conned (likely for sexually motivated killings) or met in a consensual situation (anger motivated killings; Stefanska et al. 2015) Ø Crime-phase anger: when original intention (rape or consensual sex) altered? ØAnger and blunt force trauma related (Beech et al., 2005) Ø Stranger victim: escalation studies indicate that fatal outcome more likely if victim was a stranger (e.g. Beauregard & Mieczkowski, 2012)

26 Test of Q1: Discussion of the results Ø Unusual crime scene acts: Represent enactment of deviant fantasy (Ressler et al., 1988) Ø SeSaS: to aims assess sexual sadism (Nitschke et al, 2009) q Indirect: importance of situational factors q Direct: enactment of a deviant fantasy v Correct classification (80.3%), better for indirect (85.2%) than the direct cases (75.3%), degree of noise expected in the direct group

27 Question 2. What is the relationship between level of injury in the indirect and the direct sexual killings and specific criminal event characteristics Ø Severity of attack important as it helps to understand the dynamics of the criminal event (Safarik & Jarvis, 2005) Ø Severity of the attack measured by the Homicide Injury Scale (Safarik & Jarvis, 2005) v No difference in the mean total score between the groups (t =.682, p=.49) Ø Two multiple linear regression conducted NOTE for the indirect group four outliers were identified and excluded

28 Test of Q2: Results β Sig. β Sig. Predictor Indirect Indirect Direct Direct Pre-crime anger Crime phase anger Premeditation Intoxication Use of a weapon Biting Body left as is Exertion of power, control, dominance Degrading, humiliating towards victim Mutilation of sexual parts Table 2: Multiple regressions of the severity of the attack in indirect and direct cases

29 Test of Q2: Discussion of the results Ø If severity of attack captures affect: comparable emotional intensity between the groups Comparable distribution of angry perpetrators? Difficult to define excessive violence due to anger or more predatory sadistic acts (Radojevic et al., 2013) q Indirect: crime-phase anger, intoxication, use of weapon, and body left as is on the scene Importance of situation component q Direct: crime-phase anger, use of weapon, and mutilation of sexual body parts Mixture of aggressive and offensive mutilation (Püschel & Koops, 1987) Enactment of necrosadistic fantasies (Raj et al., 1998)

30 Implications

31 q Who is a true sexual killer? We argue that direct murderer We do not imply that indirect killers are less dangerous or less culpable We argue that for the sexual homicide to be regarded as a distinct type of offence the groups would be distinguished and examined separately

32 q Are there perpetrators that are motivated by anger? Yes, but in sexual homicide this refers to first violent act We argue that angry perpetrators differ when considering sexual homicide We argue that capturing anger as a motivation does not explain the way sexual element and killing are related

33 Advantages Allows identification based on the crime scene actions Recognises that they are diverse population of perpetrators and that there would be heterogeneity even within subtypes of sexual killers Sexual homicide - a hybrid offence between sexual assault and homicide not assessing the motivation for the offending or examining if the killing was intentional ücurrent classification allows to account for how the two very important salient factors of that hybrid were related

34 Thank you