Updated

LINCOLN, Neb. -- Nebraska Gov. Dave Heineman signed a bill Thursday to change the state's method of execution from electrocution to lethal injection, although observers said it could be years before the law is applied.

Nebraska was the only state with electrocution as its sole means of execution. It had been without a means of execution since February 2008, when the state Supreme Court ruled the electric chair was unconstitutional because it amounted to cruel and unusual punishment.

Before signing the bill, Heineman noted there was "broad support for the death penalty in our state."

But the bill drew opposition from state Sens. Brenda Council and Danielle Nantkes in earlier debate. There was no debate Thursday before final approval in keeping with the practice of the state Legislature.

Nantkes predicted "significant litigation" to come, adding that she didn't think the bill did enough to spell out how executions would be performed and who would carry them out.

Senators who had opposed the measure also said it was likely to lead to more appeals for the 11 men currently on death row. The state's last execution was in 1997.

The bill, which was set to take effect Sept. 1, did not lay out a procedure for how the death penalty would be carried out. It directed the state Department of Correctional Services to develop the protocol for lethal injections.

Attorney General Jon Bruning said he expected the state would have a protocol in place within a year and be ready to request an execution date for a condemned inmate within two or three years.

Richard Dieter, executive director of the Death Penalty Information Center in Washington, D.C., said Bruning's timetable might be optimistic in light of expected civil rights and constitutional challenges in court.

"I would think it would be a while before Nebraska actually carries out one," Dieter said.

With the bill signed Thursday, Nebraska became the 36th state to use lethal injection as its primary method of execution. The Death Penalty Information Center said nine states still allow electrocution as a method.