For years, opponents of the death penalty fought about its fundamental fairness under the Constitution. When they lost that fight, they attacked the capacity of the criminal justice system to actually mete out the death penalty without bias. They lost that fight too, in the 1980s.

Now the battle over capital punishment focuses not on how defendants are convicted and sentenced, but how they are killed.

At issue in the long running dispute about lethal injections is the argument of death penalty opponents that execution by lethal injection in unconstitutionally inhumane, an argument that may be bolstered by recent botched executions, including the one Tuesday night in Oklahoma.

Clayton Lockett, a convicted murderer, died of a massive heart attack more than 40 minutes after an injection of an experimental combination of drugs failed to kill him.

Lockett’s botched execution in Oklahoma follows the controversial lethal injection of Ohio inmate Dennis McGuire who was choking and gasping for air for at least 10 minutes before finally dying more than 20 minutes after he was injected with a new cocktail of drugs in January.

In both cases the source of the drugs administered to the prisoners was kept secret under new state laws. They were enacted after a drug shortage prompted state corrections officials to seek new suppliers and experiment with different combinations of drugs. Previously, all states where the death penalty is legal used the same three-drug cocktail for lethal injection.

The rationale for the laws passed in Oklahoma, Georgia, Texas and elsewhere: protect the pharmacists who mix the drugs from being harassed — though whether they have been harassed is subject to some doubt.

Lawyers for death row inmates have argued it’s unconstitutional to block access to that information.

They assert, for one thing, that it’s impossible for anyone to know whether a drug, or combination of drugs, poses a “substantial risk of serious harm” – the Supreme Court’s standard for whether an execution method violates the 8th Amendment prohibition against cruel and unusual punishment – if the drug’s origin and effectiveness is unknown.

Some of the drugs come from compounding pharmacies, which are subject to minimal regulation. They use their own recipes and have been linked to controversy. In 2012, 64 people were killed when tainted drugs from a Massachussetts compounding pharmacy caused a meningitis outbreak.

So far none of the state secrecy laws have been overturned on 8th Amendment grounds. Lawyers have also challenged, with mixed results, the laws on other grounds. They contend that withholding information about the drugs impedes legal challenges and blocks access to courts.

In Oklahoma, the legal wrangling over Lockett’s execution and the execution of Charles Warner, which was scheduled for last night and then postponed after Lockett’s went awry, shows how politicized this issue is.

In February, the inmates filed a civil suit challenging the secrecy provision of Oklahoma’s death penalty law. An appeals court postponed their executions in mid-March because the state didn’t have the drugs to carry them out.

Then the state got the drugs but the state Supreme Court, which typically doesn’t handle criminal matters, last Monday stayed the executions pending resolution of the inmates’ lawsuit. The court issued an order saying that “as uncomfortable as this matter makes us, we refuse to violate our oaths of office and to leave the appellants with no access to the courts.”

The Court of Criminal Appeals had refused to consider the request for a delay.

Last Tuesday, Oklahoma Gov. Mary Fallin stepped in. She said the state Supreme Court was out of bounds when it stayed the execution and used her own authority to postpone it for one week.

After Lockett’s botched execution last night, Gov. Fallin postponed Warner’s execution for another 14 days and ordered the state corrections department to review its execution procedures to determine what went wrong.

Earlier this month, the United States Supreme Court declined to hear suits attacking drug secrecy in Missouri and Louisiana.

But that might not be the end of it.