There may be biblical warrant for saying Jesus referred both to an action of the devil, and specific results of his work of deception. Further, that the deceiver had to do something first, before what he did resulted in actual murder. I take the meaning of murder to be premeditated action that leads to the death of another, who otherwise would not have lost their life. The desire to kill had to arise first.
There is a saying, “Oh what a tangled web we weave, when first we practice to deceive.” The deceiver formed a plot, and it could be that such a plot began to be spun in his heart and mind long before he enacted it. Perhaps, when Jesus said, “in the beginning” he (being the Son of God) knew exactly when that spirit creature first began to desire something evil, which is what led to murder.
As the apostle James said, the starting point for death is actually an evil lust (desire) that tempts and draws forth the sin which, when finished, brings forth death. (James 1:13-15) Jesus said that looking lustfully on a woman was to commit adultery with her in that person’s heart. (Matthew 5:28) He also said, “For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies.” (Matthew 15:19) Therefore, the beginning of the first murder of the deceiver could be traced back to an evil thought, an evil desire, that would lead to action entailing lies, death and murder.
The first mention of his action entailing lies and death, then murder, is in Genesis chapter 3. The tangled web that resulted from his first, subtle lies in Eden soon stretched out to trap the whole human race. But prior to that, there had to be evil desires and thoughts, for the death the deceiver was responsible for was no crime of passion, carried out in the heat of the moment. In order to elevate himself to challenge the sovereignty of God and attempt a coup, the devil planned to bring death to the whole human race who would come from the first couple. Now, that’s what I call Genocide, with a capital ‘G’. Murder does not get any worse than such Genocide.