Linking Serial Murder

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Linking Serial Murder

• C. Gabrielle Salfati
• Department of Psychology
• John Jay College of Criminal Justice
• New York
• USA

2
Offender Profiling Research

• Classifying homicide and rape crime scenes
• Linking offender characteristics to crime scene
  types
• Cross-national comparisons
• Linking serial homicide and rape
• http//web.jjay.cuny.edu/gsalfati/

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Serial Homicide what do we know?

• Assumptions general beliefs
• All serial homicides are sexual
• Offenders have signatures
• Offenders are consistent across a series
• Most of the literature to date is based on
  assumptions of motivations that underlie all of
  these behaviours (clinical/treatment perspective)
• No empirical studies looking at if this holds up
• Problems of relying on motivation (for
  investigative purposes)

4
Linking - What do we need to know?

• Can we link crimes to each other?

How do we identify a series? How do we know the
difference between series? What criteria do we
use?
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• Can we link crimes to each other?

Crime 1
Crime 2
Crime 3
Crime 4
Crime 5
Crime 6
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Establishing the link

• Can we link crimes to each other?

Crime 1
Crime 2
Crime 3
Crime 4
Crime 5
Crime 6
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Linking - What do we need to know?

• Can we link crimes to each other?
• Can we link a series to a specific type of
  offender?

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Offender A
Crime 1
Crime 2
Crime 3
Crime 4
Crime 5
Crime 6
Offender B
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Linking - What do we need to know?

• Can we link crimes to each other?
• Can we link a series to a specific type of
  offender?
• However
• No research evidence to establish
• If offenders are consistent
• If they are, how this is displayed
• What behaviours are the most reliable to focus on

10
Consistency Issues

• Context
• Victim interaction
• Development/Maturation
• Experimentation
• Learning

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The Behavioural vs. Theme Focus

• Physical (phenotypical) vs Psychological
  (genotypical) behaviour
• E.g. gagging binding
• Separate behaviours
• But same theme of control
• (behavioural tool kits)

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Behaviour vs.Theme

• How consistent are offenders across a series,
  and in what way.
• Study 1
• Linking by using behaviours
• Study 2
• Linking by using themes

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Linking by using behaviours
Data from Washington State Homicide Investigation
and Tracking System (HITS) 450 homicide cases
committed by 90 offenders (5 cases each)
Bateman and Salfati (under review)
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The behaviours

• Objective behaviours obtained by police from the
  crime scenes.
• Chosen from the literature on homicide.
• Chosen in order to make the results from the
  study directly applicable to investigators
• 6 categories, each containing a number of
  variables
• Forensic awareness
• Body disposal
• Mutilation
• Weapon
• Theft
• Sexual activity

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Forensic awareness Control

• Crime kit
• Destroyed evidence
• Restrained/body bound
• Gagged
• Blindfold
• Face covered

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Body disposal

• Moved after homicide
• Hidden
• Openly displayed
• Posed
• Dressed
• Undressed
• Re-dressed

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Mutilation

• Burned
• Body parts scattered
• Disfigured
• Tortured
• Dismembered
• Bite marks

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Weapon

• Firearm/shot gun/rifle
• Stabbing or cutting
• Bludgeon or club
• Ligature
• Manual (hands/feet)
• Weapon brought to crime scene

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Theft

• Clothing (panties/shoes)
• Monetary value

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Sexual activity

• Sexually assaulted
• Oral by offender
• Oral sex victim to offender
• Vaginal sex
• Anal sex
• Antemortem Sex
• Postmortem Sex
• Foreign objects inserted
• Semen found

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Consistency Analysis

• Analysis aims to determine
• if the offender was performing the behaviour
• how consistent they were at performing the
  behaviour throughout their series
• Average consistency for behaviours within each
  category
• Average consistency for each of the six broad
  categories calculated
• 4/5 crime scenes 80 consistency

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Consistency in serial murder
4/5
3/5
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Consistency in serial murder
4/5
3/5
The inconsistently used types of behaviours are
Many of those that are currently being used for
linking ie signatures, sexual behaviours (using
stringent criteria)
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Linking by using themes
Data from Washington State Homicide Investigation
and Tracking System (HITS) 69 homicide cases
committed by 23 offenders (3 cases each)
Salfati and Bateman (2005) Serial Homicide An
Investigation of Behavioural Consistency.
Journal of Investigative Psychology and Offender
Profiling
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Typologies of homicide

• SSA based Crime Scene typologies of single
  homicide
• Expressive victim as person
• Instrumental victim as object
• Each theme contained a number of behaviours.
• Offenders engaged in any number or varied
  combinations of these at a crime scene.
• Current study found similar distinction between
  crime scenes in serial homicide
• Question how do we use the model to identify
  type of crime scene?

Block et al. 1998, Salfati and Canter 1999,
Salfati 2000, Salfati and Haratsis 2001, Santilla
et al 2001)
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Typologies of homicide

• SSA based Crime Scene typologies of single
  homicide
• Expressive victim as person
• Instrumental victim as object
• Each theme contained a number of behaviours.
• Offenders engaged in any number or varied
  combinations of these at a crime scene.
• Current study found similar distinction between
  crime scenes in serial homicide
• Question how do we use the model to identify
  type of crime scene?

Block et al. 1998, Salfati and Canter 1999,
Salfati 2000, Salfati and Haratsis 2001, Santilla
et al 2001)
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Do crime scenes follow a pattern?
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Do crime scenes follow a pattern?
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Do crime scenes follow a pattern?
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Can we use this for linking?

• Do offenders consistently perform the same type
  of offending behaviours across their series of
  homicides?

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Linking by theme?
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Implications of results

• Some evidence of consistency, but
• Offenders are mostly not thematically consistent
  (at least not using the current model levels of
  stringency of classification)
• This highlights considerable problems with
  linking using current understanding of consistency

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The Future

• Expand understanding of A-A-A issue
• Understand influences on consistency
• Evaluate what type of offenders are related to
  different type of series
• ie consistent series vs non-consistent series
• (Is this a particular pattern rather than a
  non-classifiable case?)
• Sexual vs non-sexual.
• Ongoing studies

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Ongoing Future Studies

• Consistency which behaviours are
  stable/influenced by victim/situation/learning
  etc. ( how)
• Single and serial
• Sexual vs non-sexual behavioural vs
  motivational
• Theft and sex
• Length of series ( change)
• Cooling down period
• Age of victim and offender
• Victim type (prostitutes, known etc)
• Measurements of consistency (length of series)
• Criminal background/ongoing crimes
• Spree murders
• Replication international different datasets
• Issue of quality of data measurements and
  reliability
• Homicide Profiling Index (HPI)

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For copies of papersEmail gsalfati_at_jjay.cuny.ed
uFor details of research on profilinghttp//we
b.jjay.cuny.edu/gsalfati/