Palimpsest is a reused manuscript on which the erased original text leaves a ghost image. The title of this episode is an important clue in solving the crime in this episode.
About halfway through the show, Callas, Stevens, and Nichols walk past a sign hanging on a brick wall. It reads, "WARNING! RETALIATION IS ILLEGAL," followed by a phone number and some illegible text. The phone number is legitimate and connects to the NYPD Deputy Commissioner for Equity and Inclusion, who is "responsible for creating, implementing and evaluating strategies throughout the New York City Police Department to ensure processes and procedures are inclusive, transparent, impartial, free of discrimination and harassment, and equitable for all members of the NYPD."
Brennan Brown (Merrill) previously played the role of Jerry Rivers in Episode 3.3 (The Gift (2003)).