Why do they sterilize the needle for lethal injections?

Odd - unless it's a precaution against the chance of a last minute reversal of the sentence and needing another injection to revive the prisoner. I don't know if reversal within the first few minutes is possible.

In cade of a stay of execution.  If the criminal died later of an infection,  the family  would have wrongful death suit. 

Correctional Officer union rules.