http://www.veganporn.com/1052277800.html
Question:
If race [is] merely [a] social [construct], [how do] forensic scien[tists] determine the difference between a white or [B]lack person's hair sample?
Answer:
http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric1.htm#Racial%20Determination
Racial Determination
A human hair can be associated with a particular racial group based on established models for each group. Forensic examiners differentiate between hairs of Caucasoid (European ancestry), Mongoloid (Asian ancestry), and Negroid (African ancestry) origin, all of which exhibit microscopic characteristics that distinguish one racial group from another. Head hairs are generally considered best for determining race, although hairs from other body areas can be useful. Racial determination from the microscopic examination of head hairs from infants, however, can be difficult, and hairs from individuals of mixed racial ancestry may possess microscopic characteristics attributed to more than one racial group.
The identification of race is most useful as an investigative tool, but it can also be an associative tool when an individual's hairs exhibit unusual racial characteristics.
http://www.apologeticspress.org/articles/2007 
