Canter's Case Study on John Duffy

THE PROFILE

Has lived in the areas circumscribed by the

1st 3 cases since 1983

Probably lived in that area at the time of arrest

Probably lives with a wife/gf, possibly no children.

Mid - Late 20's

Light Hair, About 5 feet 9 inches, Right Handed

Probably semi-skilled/skilled involving weekend work/

Casual labour

Job most likely does not bring him into contact with the

public.

Keeps himself to himself, but has 1 or 2 close mle friends. Probably little contact with women - especially at work.

Has knowledge of the railway system.

Variety of sexual actions suggests considerable sexual

experience.

Probably arrested some time between 24th October 1982 and January 1984 - This may have had nothing to do with the rape.

THIS WAS THE 1ST ATTEMPT TO USE BEHAVIOURAL

CHARACTERISTICS TO SEARCH FOR A CRIMINAL!

He was one of 2000 suspects linked to the crime by blood group.

Profiling has limited uses - due to the fact that the

usefulness of the method is questionable.

A key failure of profiling was the "Rachel Nickell

Case.

WHERE DID CANTER START?

THE PROFILE

All allowed Canter to draw up a rough profile:

LED TO...

Canter's Circle Theory of Crime

In this, Criminals are classed as either:

- Strike out from their home base

MARAUDER

COMMUTER

- Travel away from home base

to commit murders

USING A MAP

BACKGROUND

Canter suggested placing the cases on a MAP

and overlaying each year on an acetate film -

This revealed distinctive patterns in locations and types

of crimes thus allowing Canter to speculate on where

Duffy was likely to live.

1st step

In 2000, JD who was serving life for the rape and murder

of several women, confessed to many more - This was to "clear

his conscience"

Idea that Violent crime can be

seen as a transaction between 2

people. Therefore, it must tell us

something about how they deal

with people?

Last step

2nd step

Looked at how much Dominance was used.

Specifically, how willing the offender

is to try to relate to the victim - indicates

to previous similar attempts at a relationship.

Little dominance indicates a weaker

individual who is insecure

Showed that Duffy was a

MARAUDER

Also admitted to having an accomplice - DAVID MULCAHY

Overall, he admitted to 25 offences between 1975 and 1986

This was many more than the police actually had evidence for.

In the early 80's CANTER became involved, he began to draw up a

table of the cases chronologically, as well as how many it had been committed by.

This was the beginning of Canters method of Profiling

is here

CANTER - A CASE STUDY OF JOHN DUFFY

EVALUATION

Case Study - Small sample = Lower reliability.

AGE ETC.

RESIDENCE

Results

Turned out Duffy was a lot shorter than the victims described and the versions of appearance varied greatly.

Could be due to the 'weapon effect' because a knife was used to control them.

Overall memories of the actions and events of the attacks were fairly accurate and revealed the similarities in Duffy's Modus Operendi

OCCUPATION

The next step

CHARACTER

Duffy was already on the data base because he had already been interviewed in connection with an attack at knife point of his ex wife.

Profile was fed into the computer and Duffy was the only one who fit the profile.

CRIMINAL RECORD

SEXUAL ACTIVITY

He was then watched by a surveillence team and was then arrested due to suspicious activities.