This chapter examines the criminal trajectories of serial homicide offenders, distinguishing between those driven by sexual motives (sexual homicide offenders, SHOs) and those without such motives (nonsexual homicide offenders, NSOs). Using the criminal career paradigm, it explores five dimensions—participation, frequency, severity, length, and diversity—to highlight similarities and contrasts across offender groups. Evidence shows that both SHOs and NSOs often display early-onset, persistent offending, offense diversification, and escalation in seriousness over time. The second part of the chapter focuses on escalation processes among SHOs, synthesizing empirical findings on individual, relational, and situational factors that facilitate the progression from nonlethal offenses to homicide. These include prior victimization, psychosexual vulnerabilities, offender–victim interactions, institutional responses, and contextual opportunities. Adopting a longitudinal perspective, the chapter contributes to a developmental understanding of sexual homicide and its escalation, with implications for criminological theory and preventive approaches.