Many death penalty attorneys become death penalty attorneys because they oppose the death penalty, period. They do not think the state should have the power to execute a citizen or they think the criminal justice system is so inherently corrupt/biased that there is no way for a state to fairly carry out executions. Organizations like the innocence project - where attorneys fight to get cases reopened due to mistakes or misconduct - fall along the same lines. So a good DP attorney can believe their client is guilty and deserves LWOP but not want to see their client executed. It is a difficult field.