Juan Martinez began working for the Maricopa County Attorney's office in 1988. In his twenty-seven-year career with the office, he has spent nineteen years prosecuting homicide cases. Some of his most noteworthy cases include Arizona v. Wendi Andriano, who was convicted of first-degree murder and was the first woman sentenced to death by a jury in Arizona; Arizona v. Scott Falater, which was noted for the use of sleepwalking as a defense to the murder of his wife; Arizona v. Loren Wade, in which an Arizona State University football player was convicted of the shooting murder of an ex-ASU football player; and Arizona v. Rick Wayne Valentini, which resulted in a conviction for murder even though the victim's body was never found.