Featured News Estimating the age of sex offenders

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Tue, 7 Aug 2018

Estimating the age of sex offenders

A James Cook University researcher has been examining how accurately victims of sexual assault are able to estimate an offender’s age when that offender is a stranger, and what factors affect those age estimations.

Dr Craig Thorley, who is a Psychology Lecturer at JCU, led the study comparing 546 sexual assault victims’ age estimations during their initial police interviews to the convicted offender’s actual age when the assault occurred.

“Age estimations are helpful to the police when trying to identify an unknown offender as they can focus their investigation on potential suspects close to this age. It is therefore important to know how accurate these age estimations are,” he said.

Dr Thorley said few studies had examined the accuracy of these estimates.

“We made some important new findings. For example, we found victims’ age estimations were, on average, accurate to within five years of the offender’s true age,” he said.

The researchers looked at factors including whether the offender had a weapon during the assault, whether the victims had consumed alcohol, the amount of time that elapsed between the crime and the victim reporting it, and whether the offender was masked or covered the victim’s eyes.

“We found these things had no effect on the victim’s accuracy. The one thing that mattered in estimating an offender’s age was whether the offender was close to the same age as the victim. We found that victims were less accurate when the age difference between them and the offender increased.”

Dr Thorley said the leading theory for why this happens is the perceptual-expertise hypothesis, which suggests that people have most contact with members of their own age group and become experts at estimating their age.

He said the study’s findings will help investigators, and the specialists who support them, to understand sexual assault victims’ likely age estimation accuracy.

Link to paper here.

Dr. Thorley is following this research up with two short studies examining how well the public can estimate the age of strangers when those strangers are wearing different types of disguises. Anyone interested in taking part can complete the studies on the links below:


Dr Craig Thorley
P: 07 4781 6354
E:  craig.thorley@jcu.edu.au
W: www.craigthorley.com