The former ER actor will make a guest appearance in the pilot - created by CSI: Crime Scene Investigation showrunner Carol Mendelsohn - as Lieutenant Lutrell, a friend of protagonist Denny (John Corbett).
La Salle has an option for a recurring role if the show is picked up to series, according to The Hollywood Reporter.
Widow Detective stars Sex and the City actor Corbett as a detective who becomes a surrogate husband, lover and father to the families of his past partners, all of whom died in the line of duty.
Widow Detective has been written by David Hubbard, who will also take on executive producing duties alongside Mendelsohn and Julie Weitz.
Elyes Gabel (Game of Thrones, Psychoville) has already been cast as Denny's current partner, a new detective who is the son of one of the widows on the show.
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