In 2008, the U.S. Supreme Court banned the death penalty for child rapes in which a death didn’t occur, spelling out that a killing is the only crime eligible for the death penalty outside of a crime against the state such as treason.

A death penalty case against Castro “would raise serious legal questions about whether a murder has occurred and whether such a death sentence complies” with the court’s 2008 ruling, Richard Dieter, executive director of the Washington, D.C.-based Death Penalty Information Center, which opposes capital punishment, said in an email.

It’s not unheard of for prosecutors to seek capital charges even when a body hasn’t been located. But the Castro case brings up another layer of difficulty given that no human remains of any kind have been found on his property.

“How does the prosecution prove a pregnancy? How do you prove that Castro caused the termination of the pregnancy?” said Michael Benza, a Case Western University law professor who has also represented death row clients.

The prosecutor also must factor in the strain of a capital case on the three women, who could face lengthy and intrusive media attention, Benza added.