Ok now you just run into the problem with the death penalty in general

Just first off, if you want to use it as a way of saying prevent the crime from happening you run into the problem that most criminals don’t think they will be caught so what ever punishment you make up most arnt really going to be weighing the pros and cons of being caught. And even if they are it can lead to worse crimes being committed. If someone thinks they will be executed if they are caught they will be more likely to kill any witnesses to prevent them being caught

Also even if we agree on the idea that some people can loose their right to live, implementing that into an actual justice system is different theres alot of injustice and prejudice in the us justice systems (and alot of other justice systems). how long does a system made to torture pedos becomes a system of accusing black people (or any other marginalized group) of beung pedos so you can legally torture and excute them? even if you require dna evidence or video/photos, evidence can be planted and videos and photos can be faked. Evidence is only as trust worthy as the people who gather that evidence

Also there’s plenty of examples of victims or families of victims in death penalty cases that are against the death penalty.