Amnesty International Thailand published an article titled "Five facts that you may not know about capital punishment" on its website http://www.amnesty.org/en/death-penalty/myths-facts/myths Below is a summary:
Myth: The threat of execution is an effective strategy in preventing terrorism.
Fact: Those people willing to commit large-scale acts of violence aimed at inflicting terror upon a society do so knowing that they could come to serious physical harm. Therefore, they often show little or no regard for their own safety. Executions of such people often provide welcome publicity for the groups to which they belong and create martyrs around whom further support may be rallied for their cause.
Myth: The death penalty deters violent crime and makes society safer.
Fact: Evidence from around the world has shown that the death penalty has no unique deterrent effect on crime. For example, in Canada the homicide rate has fallen by 40 per cent since 1975; the death penalty was abolished for murder in 1976.
Myth: The death penalty reduces drug crime.
Fact: The use of the death penalty for drug-related crimes is in violation of international law. There is no clear evidence that the use of the death penalty for such crimes acts as a stronger deterrent than long terms of imprisonment. (In March 2008, the executive director of the UN Office on Drugs and Crime called for an end to the use of the death penalty for drug offences: “Although drugs kill, I don’t believe we need to kill for drugs.”)
Myth: Individuals are less likely to commit violent crimes if they know they will face capital punishment.
Fact: Many crimes are committed on the spur of the moment, leaving little opportunity for potential punishments to influence whether the crime is committed in the first place, as criminals do not believe they will be caught and held to account.
Myth:The death penalty is fine as long as the majority of the public support it.
Fact: It is understandable that populations look to their leaders to take decisive action against violence and express anger at those guilty of brutal crimes. Amnesty International recognises the right of nations to create laws. However, such laws must be formulated within the boundaries of respect for human rights.
Myth: Executions provide the most cost-effective solution to violent crime.
Fact: Human life should not be taken by the state on the grounds that it saves money. Using the death penalty to reduce the prison population is futile. For example, the United States has a prison population of about 2.2 million, but only around 3,000 prisoners are condemned to death. If the entire population of death row were executed, it would make no discernible difference to the prison population.