Unfortunately these inmate confessions seldom amount to much.
There were multiple confessions to the Sacco-Vanzetti murders -- every nut case around, plus the ex-cons and anarchists that tried to arrange confessions either to get off a charge or to clear S&V's names.
That was a much more politically 'hot' case than this one - it was the pet cause of every parlor pink and radical lib for 50 years. But the 'confessions' never went anywhere despite all the political pressure.