While supporters and relatives of Erik and Lyle Menendez have advocated for their resentencing and possible release from prison, current and former prosecutors who tried the brothers in the 1990s told NBC News that they believe the men are cold-blooded killers and should remain where they are — behind bars.

In an exclusive interview, one of the prosecutors cast doubt on a new piece of potential evidence the brothers have presented in court to challenge their convictions.

“They killed…