Scarver was justified. Although what Scarver did was against the law, his actions were justified in a spiritual sense for all the people Dahmer killed. He senselessly killed his victims and hurt their families deeply. This is almost an eye-for-an-eye case. Dahmer was an example of one of the worst human beings that ever lived.
This is a tricky question because yes he was justified in killing Dahmer based off what Dahmer had done. People that do things like that don't deserve to live out the rest of their lives in jail fairly comfortable or by lethal injection. There needs to be some form of fair "eye for an eye" justice with that stuff.
Christopher Scarver talks about how unrepentant Jeffrey Dahmer was about the torture and killing he inflicted upon numerous victims. Jeffrey Dahmer would reenact the killings with his food in jail by creating a person and then pouring ketchup over it as blood. Jeffrey Dahmer deserved to die inhumanely, so hopefully Christopher Scarver tortured him as well.
Christopher Scarver was not justified in killing Jeffery Dahmer because of the heinous acts that he committed because Jeffery Dahmer had already been put through trial and convicted of his crimes. Christopher Scarver had no right to kill Dahmer for any reason because he was a fellow inmate with Dahmer. Scarver should be convicted of senseless act of murder because of this.