I can't imagine the circumstances for a person to commit a crime, but it happens, I'm one of the people who prefer to destroy.
But if the circumstances arise, it is preferable to commit a perfect crime, I think that you just have to have many resources, you just have to see the percentages of solving crimes that depending on the country, that percentage can vary and many crimes go unpunished.
If I had resources, time and someone to kill, I would start studying criminology, so I know what mistakes I should not make in my objective.
The rest would be to study the most famous criminal minds and how they came to do it.
Having influence in the power extracts, that would help a lot to avoid being investigated, for example many politicians are criminals.
And finally, hands to work....