Prison authorities called off the execution after failing to find a doctor, nurse, or other person licensed to inject medications to give a fatal dose of barbiturate, said Vernell Crittendon, a spokesman for San Quentin State Prison.
"We are unable to have a licensed medical professional come forward to inject the medication intravenously, causing the life to end," he said.
CBS News legal analyst Andrew Cohen reports stopping an execution at the last minute isn't unusual, but it almost never happens for a medical reason. In this case, with the trial judge already on record as saying he believes Morales ought to get a life sentence instead of capital punishment, the complications going forward are intense, Cohen says.
"This is now a big issue in capital cases - the way the punishment actually is administered," says Cohen. "Just about a month ago, in fact, the U.S. Supreme Court agreed to hear a case about how lethal drugs are administered and whether they violate the cruel and unusual punishment clause of the 8th amendment."
"This case is going to put more pressure on judges and legislators to try to answer more effectively the questions that doctors or, in this case anesthesiologists have, about the lethal drugs that are used in executions and the impact they have on capital defendants while they are being executed," says Cohen. "It's fairly clear that the old way of doing things is going to have to change."
It is not clear when the execution will be carried out, but the delay could last for months because of legal questions surrounding California's method of lethal injection.
The 24-hour death warrant for Michael Morales was set to expire at 11:59 p.m. Tuesday. After that, state officials have to go back to the trial judge who imposed the death sentence in 1983 for another warrant.
Hearing the news of the execution's postponement - for the second time in a single day - Barbara Christian, whose 17-year-old daughter Terri Winchell was killed by Morales - called the judicial system "ridiculous" and indicated that she is angry and disappointed.
"I'm totally disillusioned with the justice system," said Christian. "We've been waiting 25 years with the expectancy that he is gonna pay for his crimes... It feels like we just got punched in the stomach."
"Any such intervention would clearly be medically unethical," the doctors, whose identities were not released, said in a statement. "As a result, we have withdrawn from participation in this current process."
The doctors had been brought in by a federal judge after Morales' attorneys argued that the three-part lethal injection process violates the Eighth Amendment prohibition against cruel and unusual punishment. CBS News correspondent Terry Okita reports some argue that two of the drugs — the paralyzing and heart-stopping chemicals — can cause intense pain.
The judge is now is expected to hold hearings in the spring on whether the three-drug method of lethal injection, as performed without anesthesiologists, amounts to cruel and unusual punishment and is therefore unconstitutional.
Last week, U.S. District Judge Jeremy Fogel gave prison officials a choice: bring in doctors to ensure Morales was properly anesthetized, or skip the usual paralyzing and heart-stopping drugs and execute him with an overdose of a sedative.
Prison officials had planned to press forward with the execution Tuesday night using the second option. The judge approved that decision, but said the sedative must be administered in the execution chamber by a person who is licensed by the state to inject medications intravenously. That group would include doctors, nurses and other medical technicians.
The state notified the 9th U.S. Circuit Court of Appeals late Tuesday afternoon that it did not intend to go forward with the execution, said Cathy Catterson, a clerk for the 9th Circuit.
Morales, who had spent the day in the prison's "death watch" cell, was relieved to learn of the postponement.
"He smiled," Crittendon said. "He nodded. He thanked me."
The judge's ruling renewed an ethical debate that has persisted for many years about the proper role of doctors in executions and the suitability of the lethal injection method used in California and 35 other states.
The American Medical Association, the American Society of Anesthesiologists and the California Medical Association all opposed the anesthesiologists' participation as unethical and unprofessional.
The anesthesiologists would have joined another doctor who is on duty at all California executions to declare the prisoner dead and ensure proper medical procedures are followed. The doctor does not insert any of the intravenous lines and is not in the room during the execution itself; typically the doctor watches the inmate's vital signs on electronic monitors outside the death chamber.
Deborah Denno, a Fordham University law professor and expert on lethal injection, said Fogel's order seemed "like a desperate measure."
"These are not circumstances by which somebody ought to be executed," she said. "It's never been done before like this."
The U.S. Supreme Court has never directly addressed the constitutionality of lethal injection or whether it causes inmates excessive pain.
Morales was condemned in 1983 for killing 17-year-old Terri Winchell, who was attacked with a hammer, stabbed and left to die half-naked in a vineyard.
Morales had plotted the killing with a gay cousin who was jealous of Winchell's relationship with another man. The cousin was sentenced to life in prison without parole.