Lydia mentions that she likes to shop in the "mall" in Wrentham because there is no sales tax. Since the Wrentham Premium outlets are in Massachusetts, all stores are subject to Massachusetts sales tax.
At the Wrentham Village Outlets (aka Wrentham Mall) there isn't a Massachusetts sales tax on clothing items under $175.
Maura finds blood in the slide of the gun used to murder Shane. Jane explains that an improper grip causes the slide to come back and cause it to cut the skin between the thumb and forefinger. When they go to arrest the father of the victim for murder they could simply rule him out by looking for a cut on his shooting hand.
Dr Isles describes a drug as "cocaine hydrochloride in the freebase form." This is contradictory: "freebase" means cocaine with the hydrochloride removed.