The growing secrecy adopted by death penalty states to hide the source of their lethal injection drugs used in executions is being challenged in a new lawsuit in Missouri, which argues that the American people have a right to know how the ultimate punishment is being carried out in their name.

The legal challenge, brought by the Guardian, Associated Press and the three largest Missouri newspapers, calls on state judges to intervene to put a stop to the creeping secrecy that has taken hold in the state in common with many other death penalty jurisdictions. The lawsuit argues that under the first amendment of the US constitution the public has a right of access to know “the type, quality and source of drugs used by a state to execute an individual in the name of the people”.

It is believed to be the first time that the first amendment right of access has been used to challenge secrecy in the application of the death penalty.

Deborah Denno, an expert in execution methods at Fordham University law school in New York, said that more and more states were turning to secrecy as a way of hiding basic flaws in their procedures. “If states were doing things properly they wouldn’t have a problem releasing information – they are imposing a veil of secrecy to hide incompetence.”

“This is like the government building bridges, and trying to hide the identity of the company that makes the bolts,” said Richard Dieter of the Death Penalty Information Center. “Those involved in public service should expect public scrutiny in order to root out problems, particular when the state is carrying out the most intimate act possible – killing people.”

A Guardian survey has identified at least 13 states that have changed their rules to withhold from the public all information relating to how they get hold of lethal drugs. They include several of the most active death penalty states including Texas, which has executed seven prisoners so far this year, Florida (five), Missouri (four) and Oklahoma (three).

Attention has been drawn to the secrecy issue by the botched execution of Clayton Lockett in Oklahoma on 29 April in which the prisoner took 43 minutes to die, apparently in great pain, from an untested cocktail of drugs whose source was not made public. Lockett’s lawyers had argued in advance that he might be subjected to cruel and unusual punishment as a result of the lack of information surrounding the drugs, but the state supreme court allowed the procedure to go ahead having come under intense pressure from local politicians, some of whom threatened to impeach judges.

In the wake of the events in Oklahoma, in which the prisoner writhed and groaned over a prolonged period, the state has agreed to pause for six months before carrying out any further judicial killings to give time for an internal investigation to be completed. President Obama described the Lockett execution “deeply troubling” and has asked US attorney general Eric Holder to review the way the death penalty is conducted.

Until last year, Missouri which is now executing prisoners at a rate of one a month, was open about where it obtained its lethal injection chemicals. But like many death penalty states, its drug supplies have dwindled as a result of a European-led pharmaceutical boycott, and in a desperate move to try to find new suppliers it has shrouded their identity in secrecy.

In October, the state changed its so-called “black hood law” that had historically been used to guard the identity of those directly involved in the death process. The department of corrections expanded the definition of its execution team to include pharmacies and “individuals who prescribe, compound, prepare, or otherwise supply the chemicals for use in the lethal injection procedure”.

Six inmates have been executed by Missouri since the new secrecy rules came in –they went to their deaths entirely ignorant of the source or quality of the drugs used to kill them. All that is known is that the pentobarbital that Missouri deploys in executions probably came from a compounding pharmacy – an outlet that makes up small batches of the drug to order in the absence of stringent regulation.

The next prisoner scheduled to be executed by Missouri, on 21 May, is Russell Bucklew, for the murder in 1996 of Michael Sanders. The department of corrections' refusal to share any information on the nature of its lethal drugs – either with the public or with the inmate’s lawyers – is particularly sensitive in his case, as he suffers from a rare condition known as cavernous hemangioma, which affects blood vessels in the head and neck.

Russell Bucklew is scheduled to be executed by Missouri on 21 May. Photograph: /AP Photograph: AP

In a telephone interview with the Guardian, Bucklew, 45, said Missouri’s secrecy suggested to him that it had something to hide. “If you don’t have anything to hide, then you put it out in the open. It’s that simple,” he said.

He was distressed by the botched execution of Lockett in Oklahoma. “Everything comes in threes, and I'm like: 'Oh shit', you know? I'm the next guy up. Am I gonna get all screwed up here? Are they gonna screw it up? And you know if anything can go wrong in Missouri, then it's gonna go wrong.”

He said it was “ridiculous” that Missouri was allowed to buy drugs from “substandard pharmacies”, adding: “And then they're shielding them from us, which I don't understand.”

Bucklew’s lawyer, Cheryl Pilate, said Missouri’s secrecy was an abrogation of her client’s constitutional rights. “Using secret drugs poses a grave risk to any prisoner facing execution, let alone someone with such a severe medical condition. This is tantamount to experimenting on a human being.”

Pilate has applied for permission to video record Bucklew’s execution. “There is a high likelihood of a protracted, painful, bloody and ugly death – and the public should know what’s being done in its name.”

The Guardian, AP and the three local newspapers – the Kansas City Star, the Springfield News-Leader and the St Louis Post-Dispatch - last month requested copies of public records relating to the state’s drug suppliers under Missouri’s transparency rules known as the “sunshine law”. The provision says that unless stipulated, “all public records of public governmental bodies shall be open to the public for inspection”.

Specifically, the news outlets asked to see records disclosing the name, chemical composition, concentration and source of the drugs approved for use in lethal injections under Missouri’s execution protocol. They also asked to see the results of any quality tests carried out on the drugs, as well as the qualifications of contractors employed by the state to provide or test the compounds.

The department of corrections declined to provide any of the requested information, saying the documents were “closed pursuant to the state secret doctrine” and citing the “black hood law”.

The Guardian has now challenged Missouri’s refusal to provide any information in the Cole County circuit court that covers the state’s capital, Jefferson City. It is is represented in the legal action by the Media Freedom and Information Access Clinic at Yale Law School, with the assistance of Lathrop & Gage LLP in Missouri.

Death penalty states have cast a veil of secrecy around the source of their drugs in a number of different ways. In Missouri and some other states, the departments of correction have unilaterally changed their execution protocols to hide the identity of drug suppliers.

In others, like Oklahoma, state legislators have amended the laws to grant pharmacies and drug distributors anonymity. In the most extreme case, Georgia, the state assembly passed a new law that turned the identity of “any person or entity that manufactures, supplies, compounds, or prescribes the drugs, medical supplies, or medical equipment utilized in the execution of a death sentence” into a state secret.

The supreme court of Georgia is currently reviewing its new secrecy law to decide whether or not it is constitutional. The state currently has no executions scheduled.