Heather and Kevin Harer didn’t have a constitutional right to a flawless investigation by police in Channahon, a town southwest of Joliet, into whether their daughter Samantha Harer was murdered by her boyfriend, a police officer in the nearby community of Crest Hill, but they asked U.S. District Judge Robert W. Gettleman for permission to file a second amended complaint against Channahon and three of its employees for …