The death penalty deters violent crime and makes society safer.
There is no convincing evidence that the death penalty has a unique deterrent effect.
More than three decades after abolishing the death penalty, Canada's murder rate remains over one third lower than it was in 1976.
A 35-year study compared murder rates between Hong Kong, where there is no death penalty, and Singapore, which has a similar size population and executed regularly. The death penalty had little impact on crime rates.
The threat of execution is an effective strategy in preventing terrorist attacks.
The prospect of execution is unlikely to act as a deterrent to people prepared to kill and injure for the sake of a political or other ideology.
Indeed, some officials responsible for counter-terrorism have repeatedly pointed out that those who are executed can be perceived as martyrs whose memory becomes a rallying point for their ideology or organizations.
Armed opposition groups have also pointed to the use of the death penalty as a justification for reprisals, thereby continuing the cycle of violence.
The death penalty is fine as long as the majority of the public supports it.
History is littered with human rights violations that were supported by the majority, but which were subsequently looked upon with horror.
Slavery, racial segregation and lynching all had support in the societies where they occurred but constituted gross violations of the people's human rights. Ultimately, the duty of governments is to protect the rights of all individuals, even though sometimes this means acting against the views of the majority.
Moreover, public opinion often changes depending on political leadership and when objective information on the death penalty is provided to the public.
All people who are executed have been proven guilty of serious crimes.
Around the world, hundreds of prisoners are executed after grossly unfair trials. This can include the use of "confessions" extracted under torture, the denial of access to lawyers and inadequate legal representation.
The countries that execute the most are also the ones where serious concerns exist about the fairness of the justice system, such as in China, Iran and Iraq.
The 144 exonerations of death row prisoners recorded in the USA since 1973 show that, regardless of how many legal safeguards are in place, no justice system is free from error. As long as human justice remains fallible, the risk of executing the innocent can never be eliminated.
Relatives of murder victims demand capital punishment.
The worldwide anti-death penalty movement includes many who have lost their loved ones to, or have themselves been victims of, violent crime, but for ethical or religious reasons do not want the death penalty imposed "in their name". In the USA, organizations such as "Murder Victims' Families for Human Rights" are driving the movement to abolish the death penalty, for example, in New Hampshire.