“I was taught that ‘thou shalt not kill’ should be translated ‘thou shalt not commit murder.’ Any help on that issue?”
This is often taught to make Exodus 20:13 compatible with the capital punishment taught in Genesis 9:6. But the Hebrew word for “kill” in Exodus 20:13 is sometimes used in reference to committing manslaughter (Num. 35:6,12), which is not the same as murder.
The compatibility of Genesis 9:6 and Exodus 20:13 is always found in the context of verses that seem to suggest they are incompatible. God sees a difference between murder and manslaughter (Num. 35:15-23). He also sees a difference between the cold-blooded murder of an innocent victim and the orderly execution of a guilty murderer by the government.