To be very clear, I don't agree with what some of Ohio's politicians are trying to do and I really don't agree with the death penalty!
Nowt says “pro-life” like suggesting the death penalty for abortion.
Many 'pro-lifers' are Christian fundamentalists (not all, but huge numbers), here's how they'd justify their (horrific) viewpoint:
The word 'kill', as used in Exodus 20:13 KJV bible is taken from the Hebrew for murder - you must not murder i.e. take a life without just legal cause.
The word 'kill' as used in Ecclesiastes 3:3 was translated from a different Hebrew word and means to kill/slay (not murder).
Therefore, with eyes firmly attuned to a hell-fire-and-brimstone interpretation of the bible, taking the life of the fetus would be adjudged murder as it would have no legal cause. The death penalty would have legal cause as this right was conferred upon governments by God (Romans 12 through Romans 13).
All of which does a sickening job of turning the bible into what the fundamentalist movement want it to be - with scarily little appreciation for the teachings of Christ.