Among the evidence that the forensics department found at Gina's apartment was hair belonging to Mario Lopez. Gina says she once purchased a lock of Lopez's hair. Setting aside how long DNA analysis actually takes, it is virtually impossible to identify someone from hair without the root attached. While some strides have been made in recent years, DNA fragments in the hair shaft itself are still generally unsuitable for using to identify a person based on DNA alone.
Captain Holt wears his Commendation breast bar above his World Trade Center Breast Bar. When the WTC bar is worn, it is worn above all other medals, but below the American Flag bar.
During the briefing about CompStat numbers, there is a case on the whiteboard credited to "Detectives Diaz and Jefferds." Not only is Terry Jeffords' last name misspelled, but he is a sergeant, not a detective.