In 2011, a Franklin County man charged under Ohio's fetal homicide law was sentenced to 13 years in prison for taking his pregnant girlfriend to an abortion clinic at gunpoint.
In 2008, a Stark County jury convicted former police officer Bobby Cutts of killing his pregnant lover and their nearly full-term unborn daughter but gave him life in prison instead of a death sentence.
Cutts unsuccessfully appealed the verdict on the grounds that a conviction of murder for the death of his lover was inconsistent with a conviction of aggravated murder for the death of the fetus.
Earlier this month in Pennsylvania, an abortion doctor convicted of killing babies born alive at his clinic avoided a possible death sentence by waiving his right to appeal in exchange for a sentence of life without parole.
Prosecutors argued that Dr. Kermit Gosnell killed the babies after they were born, not as fetuses. Gosnell argued that none of the fetuses was born alive and that any movements they made were posthumous twitching or spasms.
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.
The nature of the crime makes it likely that, death penalty or not, Castro would face a life sentence if convicted on rape charges alone, said Hofstra University law professor and death penalty expert Eric M. Freedman.
"The odds that it's going to go to a death penalty trial and result in a jury verdict of death," he said, "are vanishingly small."