An American politician wants to bring back the death penalty in his home state and is proposing the lethal injection be filled with heroin and fentanyl, the synthetic opioid at the heart of a US drugs death epidemic.

The last execution in Maryland was in 1993 and death sentences were officially outlawed in 2013, but Republican Senator Robert G. Cassilly thinks that should change in the wake of a mass shooting on 18 October.

Multiple felon Raddee Prince, 37, is accused of killing three co-workers and wounding two others at a kitchen surfaces manufacturer in Delaware. He faces a slew of charges including first-degree murder and if convicted will be jailed for life without parole.

"It's just outrageous that we as citizens of the state of Maryland are unable... to extract appropriate justice for such a heinous act," Cassilly said, at a press conference on 23 October.

"There's got to be a penalty that says, 'Look, you've killed; now it can actually get a whole lot worse from this because we will hold your life over your head'," he added, as reported by Patch.com.

Cassilly then explained that objections to lethal injections on grounds of pain could be dismissed if convicts were given heroin and fentanyl in high doses. He argued that opioid users' willingness to chase more hits even after they had come close to death proved that the injections "obviously must not be too painful".

Opioids are respiratory inhibitors that block the brain from telling the body to breathe. When taken in high doses users effectively forget how to breathe. Fentanyl is so powerful – 100 times stronger than heroin – that just a few grains can kill a person. The increased prevalence of fentanyl-laced heroin has been a significant factor in the US opioid crisis.

Maryland State Attorney Joseph Cassilly – the Senator's brother – claimed that lethal injections composed of opioids would send a strong message to drug users in the state, saying: "That's a point to be taken about how deadly that combination is."

Fentanyl heroin opioids
Fentanyl-laced heroin ready for consumption RENDAN SMIALOWSKI/AFP/Getty Images

In September, the state of Nevada announced plans to use fentanyl in lethal injections following a trend of pharmaceutical companies refusing to sell traditional execution drugs, such as midazolam and hydromorphone, to prisons.

The proposals, first reported by The Marshall Project, are intended for the execution of murderer Scott Raymond Dozier later in November. He will be injected with a cocktail of fentanyl, Valium and cisatracurium.

Joel B. Zivot, an Emory University anesthesiologist was critical of the thinking behind the combination. He said: "This is not actually science,. It's not actually medicine. It is a grotesque impersonation of those things."