On Friday the NBC News show “Dateline” will air an hour-long episode on the murder trials of Cara Rintala, who was found guilty of killing her wife by a Hampshire County jury in October. It took 13 years and four trials for Rintala to be found guilty of killing Annamarie Cochrane Rintala by strangulation, then attempting to obscure evidence by covering them both in paint at the bottom of the basement stairs. The first two trials resulted in a hung jury, and the third ended with a conviction overturned by the state Supreme Judicial Court due to an impermissible witness testimony. The Dateline episode airs on Friday at 10 p.m.