Last week's execution by the US state of Texas of a convicted murderer described as having an IQ of less than 70 has put the spotlight there on the death penalty, and raised questions about the issue of culpability.
Marvin Wilson (54) was convicted of the November 1992 murder of a 21-year-old police drug informant, Jerry Robert Williams, and in April 1994 sentenced to death.
He was the 25th person to be executed in the US this year, according to figures from the Death Penalty Information Centre.
Wilson challenged his execution as unconstitutional under a 2002 Supreme Court ruling that banned executing a person of diminished intellectual capacity, but which also gave states the responsibility of defining that threshold.
The Eighth Amendment to the United States Constitution forbids "cruel and unusual punishments", and the 2002 court ruling stated the Eighth Amendment should be interpreted in light of the "evolving standards of decency that mark the progress of a maturing society".
The court held that "execution of offenders with mental retardation is unconstitutionally excessive".
A test showed Wilson's IQ was 61, below the 70 level sometimes used as the standard, but Texas argued the test was flawed and that other tests showed an IQ above 70.
The court denied Wilson's application.
Wilson's lawyer, Lee Kovarsky, said of the execution: "I hope that, at the very least, something like this occasions some serious reflection on what it means to be culpable."
The issue of culpability is particularly pertinent in respect to a person of diminished intellectual capacity. It can and is argued that these people - much like children - may commit crimes or other actions without fully appreciating their implications or morality.
They are often more disposed to want to "please" others and might be swayed to confess to actions for that reason, again possibly without realising their implications.
One of the arguments against the death penalty is the possibility an innocent person could be executed, and certainly miscarriages of justice have occurred, and convictions overturned.
Figures show that, since 1973, more than 130 people in the US have been released from death row after evidence of their innocence.
Of course, there are crimes in which the evidence of a person's guilt is irrefutable, whether through forensic evidence or eye witnesses.
But even in such cases, courts will take into account the psychological states of perpetrators, and there is often debate around their upbringing, and other environmental and social factors, which can sometimes make a guilty verdict less "cut and dried" and provoke debate about nature and nurture and discussion about whether people are "born evil" or "made evil".
But regardless of the crime committed - and this is not to condone crime, especially of a violent nature, or to lessen its horrific impact on victims and their loved ones - the death penalty appears to be an irreconcilable punishment for a state that deems murder a crime, but is then itself prepared to take someone's life.
If a society is judged on how it treats its most vulnerable, such as those with diminished intellectual capacity, that surely includes those facing losing their life - even as a result of taking someone else's.
It is also worth considering the Eighth Amendment - "cruel and unusual punishments" - in light of the death penalty in general.
Surely, it is the ultimate cruelty to deprive anyone of life - even a convicted criminal who may have cut short the life of their victim.
The test seems to fail at a fundamental level for any state that considers itself fair and reasonable and desirous of following the "evolving standards of decency that mark the progress of a maturing society" as highlighted in the 2002 Supreme Court ruling.
For the loved ones of murder and manslaughter victims, their need for ultimate justice and retribution - an eye for an eye, a life for a life - is understandable.
So, too, is the reaction of many in general society.
But is it not also worth remembering that meaningful prison sentences - which ensure justice, punishment, deterrence and public safety - can be served, without recourse to the death penalty?
