Robert Cole is a local peeping tom at Riverside Park who spies on women and bonds with them by pretending to taking pictures of their kids just to flirt with them and ask them for their phone numbers, hoping to find suitable women to start relationships with.
When Marty Willick was pleading to a cop he lost his infant daughter Emily in the same park, detectives tried to look for suspects and heard about Robert's activity. They confiscated his camera and saw it has no film in it, them found his notebook he kept women's phone numbers in. This cleared him of suspicion, especially after Emily was found dead when Marty admitted to buying her after she died. (L&O: "Precious")