If there was someone I hated, truly hated and wanted them dead, I would kill them.

As long as it was a well thought out plan, the odds of me getting away with it are pretty decent. The only consequence is jail, nothing in the afterlife. So if I'm confident enough that I can get away with murder, I would do it. I wouldn't do it, if I knew that as soon as I died I was going to be judged for it.

There are more people that think this way, than you think.

Most murders aren't well thought out, and there are some murders that are unsolved. If I were to plan out a murder, making sure to leave no DNA, witnesses, evidence, it makes proving a murder very difficult. I'm not saying I would get away with it, but there is a good enough chance to risk it if you hate a person enough and won't be judged after death.