Here are observations from one commentary found at biblegateway:
John portrays the devil as exactly the opposite of Jesus. Here the devil is described with respect to a beginning (v. 44), as is Jesus also (1:1). But Jesus is life (14:6) and has life in himself and gives life (1:4; 5:26), whereas the devil is a murderer (v. 44). Furthermore, the devil was not holding to the truth (more literally, "did not stand in the truth," en te aletheia ouk esteken), because there is no truth in him (v. 44). In John's thought "truth" (aletheia) "means eternal reality as revealed to men—either the reality itself or the revelation of it" (Dodd 1953:177). These two aspects of truth are united in Jesus who both is the truth (14:6) and speaks the truth (8:40). Just as it is Jesus' very nature to be the truth, so it is the devil's very nature to lack the truth and speak lies, for he is a liar and the father of lies. So John depicts the devil as the personification of what is the exact opposite of Jesus.
The three main characteristics of the devil in this verse move from the exterior to the interior, as it were. The first description is of the devil's external activity as a murderer. This is followed by a general reference to his alienation from the truth. The description concludes with the assertion that this alienation from the truth is thorough; to his very core there is no truth in him, but rather lies. Thus, John is pointing to the inner core of the devil just as he points to the heart of the opponents.