Forensic Hair Examination

Question 1

Describe the terms ‘sensitivity’ and ‘specificity’

Answer 1

SENSITIVITY - true positive rate

SPECIFICITY - true negative rate

PRECISION - positive predictive value = proportion of true positives against all positive results

NEGATIVE PREDICTIVE VALUE - proportion of true negatives against all negative results

ACCURACY - proportion of true results

Question 2

Define the terms ‘transitional hairs’, ‘buckling’ and ‘shouldering’

Answer 2

TRANSITIONAL - those on the stomach between the chest and pubic region

BUCKLING - abrupt change in direction of the hair shaft with or without a slight twist

SHOULDERING - asymmetrical cross section of hairs

Question 3

Describe the 3 phases of hair growth

Answer 3

ANAGEN - active growing phase

CANTAGEN - resting phase after active growth = follicle shuts down cell production and root bulb forms

TELOGEN - resting phase for follicle = complete lack of cell production