Green disappeared sometime in March 2000 from her residence on Lock Avenue in Sacramento, California. Three months after her disappearance, investigators received a call from a man who said he had been told that Green had been murdered and her body disposed of. It was only then that they realized Green was missing. Though they were unable to divine further information at the time, police opened an investigation and classified her case as a homicide. Green's three-year-old daughter was located at a residence in North Sacramento on July 9, 2000, and was placed in protective custody. In August of that year, Helen M. Tibon and her brother, Kevin Clark, were charged with Green's murder. Clark is the father of Green's child.

Tibon and Clark were both convicted of first-degree murder in 2002. Prosecutors alleged that Green had been killed to keep her from telling police about the defendants' involvement in a lucrative mail fraud scheme. Tibon and Clark's three alleged accomplices testified against them and reported that Green was tortured before being smothered in bubble wrap. Her body was allegedly dismembered, burned, and dumped in the Sacramento River inside a metal drum. It has never been located.

Sentencing for Tibon and Clark was delayed because they told the judge they were innocent and Green was still alive. The defendants produced two letters that had been sent to them while they were in custody. Both letters were signed "Kristy Green" and one was quoted as saying, "They can't keep you in jail for a crime that never occurred." Handwriting tests on the letters were inconclusive. Two witnesses also testified, claiming to have seen Green alive after her alleged murder. On the basis of this evidence, Clark and Tibon asked for a new trial. However, the judge rejected the request, saying even if the new evidence were presented to a second jury, Tibon and Clark would still be found guilty. Both defendants were sentenced to 25 years to life in prison.

Green remains missing. Foul play is suspected in her case due to the circumstances involved.