Can you build a foolproof death penalty?

Getting tough on crime is a staple theme for many a politician. But here in Massachusetts, which hasn't executed an inmate in 56 years, Gov. Mitt Romney is pushing capital punishment with a provocative new twist.

Advances in forensic science, he argues, have made it possible to adopt a death-penalty system so reliable that innocents on death row can be made a thing of the past.

"Just as science can be used to free the innocent, it can be used to identify the guilty," Mr. Romney said recently.

It's a controversial thesis, coming at a time when the American public is rethinking the death penalty after certain death-row inmates have been exonerated and several reports have found persistent racial disparities. Yet Romney is trying to move one of the nation's most liberal states - one of 12 without the death penalty - in the opposite direction.

So last month, the Republican governor appointed a council of scientific and legal luminaries to study how to build a more perfect death-penalty statute. Reestablishing the death penalty, he argues, would serve as an important deterrent for those individuals responsible for the most heinous and violent crimes.

Joseph Hoffmann, an Indiana University law professor and cochair of the council, says the goal is a death-penalty system so reliable that he'd stake his own life on it. "Obviously, in a theoretical sense, no human endeavor can be said to be perfect," he says. "At the same time, it's quite fair and accurate to say that there is a [higher] level of certainty and a level of confidence that we can aspire to."

Similar commissions established elsewhere, however, have highlighted the limits of DNA evidence and suggest a foolproof death penalty remains out of reach.

"There's no question the death penalty can be made better," says attorney and author Scott Turow, who served on the Illinois Commission on Capital Punishment. "But we will still convict a certain number of innocent persons."

Thirteen states have appointed independent commissions to study their death-penalty statutes in recent years. Their recommendations suggest that DNA evidence is not a panacea for what lands innocents on death row.

One problem is that only a fraction of homicides involves DNA evidence. Murders ranging from a drive-by shooting to the Oklahoma City bombing leave no DNA at the crime scene.

"We assume DNA evidence is available," says William Alexa, a former Indiana state senator and current judge who served on Indiana's committee. "That's not always the case."

Where DNA evidence is part of a case, forensic scientists may still mishandle it, as scandals in Oklahoma and the FBI crime lab have proved. "There is a public perception that DNA is the cure-all for these kind of mistakes," says Richard Dieter, executive director of the Death Penalty Information Center in Washington. "DNA is not the whole answer."

There are a variety of reasons the wrong person may be convicted, such as incorrect eyewitness identifications and false confessions, the Illinois panel found.

That's why the commission's 83 recommendations included proposals that no death sentence be imposed when there is only one eyewitness and that detectives videotape homicide interrogations. Illinois has since begun requiring police departments to videotape all homicide interrogations.

Even when guilt is certain, the decision about who is sentenced to death may be arbitrary. Studies show that whether two defendants who commit similar crimes are sentenced to death may vary according to who prosecutes them and the race of the victim.

In Illinois, for example, there are 20 circumstances that might result in a death sentence. A majority of the Illinois commission suggested reducing the number of criteria to five narrow ones such as police killings, multiple murders, and torture.

Officials involved in the Massachusetts council say they're aware of those broader concerns. Mass. Lt. Gov. Kerry Healey told the Monitor that a focus on forensic science is "not the exclusive goal" of the council. And Mr. Hoffmann says that whatever recommendations the council makes, they will put greater demands on prosecutors and police, limit the type of murders that qualify for the death penalty, and demand a higher level of proof. "Going to a punishment that is irrevocable requires a level of certainty beyond what we've ever had before," he says.

One additional challenge for the Massachusetts council will be time: It has only three months in which to work, compared with two years in Illinois and 18 months in Indiana, which included lengthy investigations and empirical studies.

Massachusetts' officials say the shorter time frame is realistic since they'll have the benefit of past commissions' research and recommendations. "We will stand on their shoulders," says Ms. Healey.

At the council's first meeting at the State House in Boston, commissioners received copies of the Illinois report.

Even so, commissioners from other states warn the goal must be lower than perfection. "You'll always have a chance for error," says Mr. Alexa of Indiana. "But we think our system minimizes that risk to make it acceptable."