Yes, Adam and Eve were mortal before they sinned. They were mortal in that they physically could have died even though they had not yet sinned. Mortality was a possibility, but not a necessity in their case. If, for example, Adam had fallen out of one of the trees and had injured himself sufficiently, he would’ve died. His body was not indestructible. He had lungs, a heart, kidneys, liver, etc. The same would, of course, apply to Eve. She also had a physical body with functioning organs, and if she had sustained an injury of sufficient severity, she also would have also died. However, this works with the idea that an accident might have been possible in that pre-fallen condition (counterfactual). But, the implication is that such an accident does not seem providentially possible in a pre-fall state (counterfactuals can only exist if God ordains them). God is sovereign and it would seem fair to say that such an accident would not have been allowed by God. So, in that sense, no he could not have died. Think about this. Jesus did not have a fallen nature, yet he had the potential of dying by being killed physically. He possessed immortality but had the potentiality of dying – under the right conditions (counterfactuals). If He had not been executed by others, He would have lived forever.

On the other hand, barring an unforeseen accident, neither Adam nor Eve would have died because the effects of sin were not yet a reality and death had no place. Therefore, there was no decay, no plague, no sickness, etc., all of which did not occur until after sin entered the world through Adam (Rom. 5:12). Sin causes a separation between God and ourselves in the spiritual sense (Isaiah 59:2), and it causes separation between the spirit and the body in the physical sense through death (Romans 6:23).

So it would appear that before Adam and Eve sinned they were immortal in that given normal circumstances, they would have lived forever since the effects of sin were not on them or their environment. But, at the same time, their bodies were capable of dying physically if there were an accident of sufficient severity.

• “But your iniquities have made a separation between you and your God, and your sins have hidden His face from you so that He does not hear,” Isaiah 59:2).
• “Therefore, just as through one man sin entered into the world, and death through sin, and so death spread to all men, because all sinned,” (Romans 5:12).
• “For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord,” (Romans 6:23).