WASHINGTON (AP) - Death row inmates in more than a dozen states are fighting lethal injection, and with surprising success. What once appeared to be a long-shot legal argument now seems to be gaining ground.

Judges from California to Louisiana, and even at the nation's highest court, are entangled in disputes between state prison officials and inmates who claim their executions may be painful.

The eventual outcome of the cases could be sweeping because every state that has capital punishment, except for Nebraska, has lethal injection. Nebraska uses only the electric chair.

An emerging issue is the role of medical professionals in ending the lives of prisoners, providing an unprecedented behind-the-scenes look at jailhouse executions.

The Supreme Court refused this month to let Missouri put to death an inmate despite the state's assurances that it uses a board-certified surgeon to mix the drugs and insert intravenous lines into the prisoner's groin. The inmate claims that the doctor, whose name is kept secret, would violate medical ethics.

Earlier this week, California postponed an execution because no doctor or nurse would agree to administer a fatal dose of barbiturate. A judge is reviewing the state's system.

Based on the experience of other states, California, which has 650 condemned inmates, could be in for a long delay in executions.

In Louisiana, no inmates have been executed since 2002 as the state contests a lawsuit over the training of its executioners and the mix of drugs used. New Jersey, where a moratorium is now in place, was ordered by a state court two years ago to reconsider its procedure.

Although lethal injection does not appear to be in jeopardy, states could face new requirements for drugs and training. Legal battles are ongoing in California, Florida, Indiana, Kentucky, Louisiana, Maryland, Missouri, New Jersey, North Carolina, Ohio, Oklahoma, Tennessee, Texas and Virginia, according to anti-death penalty groups.