A University of Nebraska law professor says even though the state proved it could carry out a lethal injection execution, questions remain about the method it used.

Nebraska used a four-drug protocol to put Carey Dean Moore to death Tuesday for the shooting deaths of two Omaha cab drivers in 1979.

Professor Eric Berger points out the protocol had never been used before and had never come under the scrutiny of the courts.

Berger says the state will have to overcome several challenges if it plans to execute any other inmates on death row.

Berger says Nebraska needs to release its records of the Moore execution, so experts can determine if it went as well as it appeared to go.