Read the following description from a field observation report and answer the question that follows.
'At 11:30 hours, I observed a male subject loitering near the west entrance of the Grand Central Market.
The subject was approximately 5'10", medium build, wearing a black hooded sweatshirt, faded blue jeans, and white athletic shoes.
He was carrying a green backpack over his right shoulder.
He had short brown hair and a noticeable scar above his left eyebrow.
After a few minutes, he met with a second individual, who was wearing a red baseball cap and a grey jacket.
The two spoke for less than a minute before walking northbound on Hill Street.'
Which of the following was a specific, unique identifying feature of the first subject observed?
