Marv survived the electric chair - that's the only explanation

there is no other way to explain how he's alive after Nancy got her facial scars.

(in the first movie when he last seen her she had no scars and then he was imprisoned and executed)

so the only explanation is that the electric chair didn't kill him, only stop his heart for a short while.

the doctor examined him and declared him dead. then he woke up in the morgue and escaped. and went right back to the same bar he always goes to.

so Marv is still alive and well