The chief state’s attorney has announced that the prosecution will not attempt to retry Kennedy cousin Michael Skakel in the decades-old killing of Greenwich teen Martha Moxley. The state’s top prosecutor said the case could not be proven beyond a reasonable doubt. A key witness in the case has died. Skakel was convicted in 2002 and spent more than a decade behind bars, but his conviction was later thrown out. 15-year-old Martha Moxley was last seen alive the night before Halloween in 1975. Her body was found a short distance from her Greenwich home. Outside of court today, her brother said he believes Skakel killed his sister, but he is at peace with the decision not to seek another trial.