Capital punishment, also referred to as the death penalty, is the judicially ordered execution of a prisoner as a punishment for a serious crime, often called a capital offence or a capital crime. In those jurisdictions that practice capital punishment, its use is usually restricted to a small number of criminal offences, principally, treason and murder, that is, the deliberate premeditated killing of another person, or, even more commonly in recent years, killings that occur during the course of some other violent felony, such as robbery or rape. Prisoners who have been sentenced to death are usually kept segregated from other prisoners in a special part of the prison, pending their execution. In some places this segregated area is known as Death Row.
The term capital comes from the Indo-Europeankaput, meaning "head", through the Latincapitalis. Thus, capital punishment is the penalty for a crime so severe that it deserves decapitation (losing one's head).
In medieval Europe, the method of execution would depend on the class of the party to be executed. The ruling class nobility would usually be executed in as painless and honorable a method as possible. Working class serfs and peasants would usually be executed publicly, in a more gruesome and painful method of execution.
According to Amnesty International's annual report on official judicial execution, in 2003 there were 1,146 executions in 28 countries. 84% of the deaths occurred in four countries. The People's Republic of China (PRC) carried out 726 executions. Iran killed 108 people, the United States 65 and Vietnam 64. For the period of 1990-2003, the average number of executions per year was 2242 as reported by Amnesty. The PRC has executed at least 20,000 between 1990 and 2001 with 1,781 people executed between April and July 2001 in a "Strike Hard" crime crackdown.
Phyllis Schlafly provides a much higher count of executions in China than Amnesty International:
"...every year China has nearly 10,000 death penalty cases that result in immediate execution. That is five times more than all death penalty cases from other nations combined. China's executions have always been a closely guarded state secret, but these totals were revealed by Chen Zhonglin, a National People's Congress delegate." 
The highest per capita use of the death penalty is Singapore, with a population of about four million and an average of 70 executions per year, mostly for drugs offenses. Executions by hanging occur on Friday mornings in Changi prison.
In most countries that have capital punishment, it is used to punish only murder and/or for war-related crimes. In some countries, like the People's Republic of China, some non-violent crimes, like drug and business related crimes, are punishable with capital punishment.
Most democratic countries today have abolished the death penalty, such as Canada, Australia, New Zealand, almost all of Europe and much of Latin America. The last execution in the Republic of Ireland took place in 1954 and in 1990 it was removed from the penal code. A heated debate on whether to reintroduce capital punishment led in 2001 to a referendum which amended the Irish Constitution to make reintroduction of the death penalty unconstitutional. The Republic of Ireland thereby became the first country in the world to constitutionally ban the death penalty by popular referendum. The last execution in the United Kingdom occurred in 1964 (see Capital punishment in the United Kingdom). Russia has had a moratorium on the death penalty since 2001. In all, 80 countries have abolished it altogether (this includes Turkey), 22 countries have not executed someone in the last ten years and 14 only have the death penalty for 'exceptional crimes' (for example war crimes). Many other countries retain it, especially in Africa, the Middle East, Asia, the Caribbean, Japan and the United States, with a total of 78 countries still having the death penalty.
The most comprehensive source lists less than 15,000 people executed in the United States or its predecessors between 1608 and 1991. More accurate statistics list 4661 executions in the U.S. in the period 1930-2002 with about 2/3 of the executions occurring in the first twenty years. Additionally the U.S. Army executed 160 soldiers between 1930 and 1967. The last U.S. Navy execution was in 1849. (See also: Capital punishment in the United States)
Only seven countries practice the death penalty for juveniles, that is criminals aged under 18 at the time of their crime. Nearly all actual executions for juvenile crime take place in the USA, although, due to the slow process of appeals, no one under age 19 has been executed recently. In the United States the death penalty cannot be applied to criminals under age 16 and higher ages are legislated in many states. In the United States and ancestor bodies politic since 1642, an estimated 364 juvenile offenders have been put to death by states and the federal government. Although the People's Republic of China accounts for the vast majority of executions in the world, it does not allow for the executions of those under 18.  Execution of those aged under age 18 has occurred in the Democratic Republic of the Congo, Pakistan, Yemen,
Saudi Arabia, Nigeria, and Iran since 1990. 
The United NationsConvention on the Rights of the Child, which forbids capital punishment for juveniles, has been signed by all countries except the USA and Somalia, so it is likely that legally, the execution of persons for crimes committed as children (as defined by the Convention) will be restricted to the USA.
Several international organizations have made the abolition of the death penalty a requirement of membership, most notably the European Union and the Council of Europe. The European Union requires outright abolition of the death penalty by states wishing to join; the Council of Europe also requires this, but is willing to accept a moratorium as an interim measure. Thus, while Russia is a member of the Council of Europe, and practices the death penalty in law, it has not made use of it since becoming a member of the Council.
The same was also true of Turkey, but in August 2002, as a move towards EU membership, the death penalty was removed from law as well as practice, but only during peacetime. On November 12, 2003, Turkey ratified the Sixth Protocol of the European Convention on Human Rights. In January2004 Turkey signed the 13th Protocol, intending to abolish the death penalty completely, including during wartime . As a result of this, Europe is a continent free of the death penalty in practice (all states having ratified the Sixth Protocol), with the sole exception of Belarus, which is not a member of the Council of Europe. The Parliamentary Assembly of the Council of Europe has also been lobbying for the Council of Europe observer states who practice the death penalty (namely the United States and Japan) to be told to abolish it also or lose their observer status.
Torture and cruelty are wrong. Many executions are botched and the executed suffer extended pain in dying, and even those who die instantly suffer extreme mental torture leading up to and during the preliminaries of the execution process.
Criminal proceedings are fallible. Many people facing the death penalty have been exonerated, sometimes only minutes before their scheduled execution. Others, however, have been executed before evidence clearing them is discovered. Whilst criminal trials not involving the death penalty can involve mistakes, there is at least the opportunity for mistakes to be corrected.
Since in many cases at least the defendants are financially indigent and therefore end up being represented by court-appointed attorneys whose credentials are often highly questionable, opponents argue that the prosecution has an unfair advantage; however, in recent years some death-penalty advocates have gone on record as being open to the concept of using the French "inquisitive" system for capital cases instead of the "adversarial" proceedings currently followed in virtually all American courts today, thus addressing this issue. In addition, some states that have the death penalty - most notably New York State - have established an office of "Capital Defender," either appointed by the state's governor or popularly elected.
Additionally, it is argued that the race of the victim can also affect the likelihood of the application of the death penalty, which again is unfair - although death-penalty advocates counter this by pointing out that most murders where the killer and victim are of the same race tend to be "crimes of passion" while inter-racial murders are usually "felony murders;" that is to say, murders which were perpetrated during the commission of some other felony (most commonly either armed robbery or forcible rape), the point being that juries are more likely to impose the death penalty in cases where the offender has killed a total stranger than in those where some deep-seated, personal revenge motive may be present.
It can encourage police misconduct as in the incident described in the documentary film The Thin Blue Line. In the late 1970s, an innocent man named Randall Adams was framed by the Dallas County police department in Texas for a notorious murder of a police officer because they knew the more likely suspect, David Harris, was still a minor and thus ineligible for the death penalty so Adams had to serve as a scapegoat to execute.
It is not a deterrent because anyone that would be deterred by the death penalty would already have been deterred by life in prison, and people that are not deterred by that wouldn't be stopped by any punishment.
It has also been argued that the death penalty does not deter murder because most murders are either "crimes of passion" or are planned by people who don't think they'll get caught (however this argument could be used for any penalty)
Some people argue that the death penalty brutalises society, by sending out the message that killing people is the right thing to do in some circumstances.
Abolitionists variously argue that statistics show the death penalty either makes no difference to the number of murders, or actually causes them to increase
With mandatory appeals and enhanced procedural and evidentiary requirements for capital cases in the USA, the cost of a death penalty case far exceeds (usually by a factor of ten) the cost of a trial and life imprisonment.
Executed "terrorists" may become "martyrs"
Different groups of death penalty opponents favour different arguments. Core death-penalty opponents are perhaps more likely to primarily base their opposition on "the death penalty is murder" arguments, and advance the issues of wrong convictions and ethnic bias to convince waverers.
Key arguments for supporters of the death penalty include:
People committing the most heinous crimes (usually murder, in Western countries that practice the death penalty) have forfeited the right to life.
Government is not an individual and is given far more powers.
Death Penalty shows the greatest respect for the ordinary man's and especially the victim's inviolable value.
It strikes fewer "innocent persons" than alternative penalties, as among imprisoners and ex-prisoners there are many who relapse into new crimes which strike "innocent persons".
It provides peace of mind for many victims of crime and their families.
It recognizes humankind's natural sense of justice.
It is in fact less cruel than prolonged sentences of imprisonment, especially under the conditions that would be popularly demanded for heinous criminals.
It is explicitly allowed in constitutions and other documents of basic law.
It provides extra leverage for the prosecutor to deal for important testimony and information.
It shows how seriously society looks at the most heinous crimes.
It is the most effective deterrent of violent crime and murder. (Death penalty opponents consider this argument as discredited, see however the discussion on Pro Death Penalty Webpage.)
There is ongoing debate whether capital punishment reduces crime rates, because potential murderers (or other criminals) would be too scared of punishment to commit crime, or it doesn't affect crime rate, because potential criminals think that they won't be caught, so they don't care about punishment until it's too late. There are even studies that have concluded that the death penalty appears to encourage murder. However, like many questions in the social sciences, actual research data on this question can be (and is) interpreted very differently by people with differing predispositions towards capital punishment. In any event, the actual effectiveness or otherwise of it is largely irrelevant to many who feel strongly about the debate, as their views are based on other factors.
The Tanakh prescribes the death penalty for a great many violations of law. Most historians no longer accept the view that the laws of the Bible, as written, were ever actually followed as a legal code. Instead, they hold that the laws in the Bible were developed in a living society and culture, and that the oral law of this society was not identical to what one would posit from a literal reading of the Biblical text alone. Rabbinic Jews have always held this view; Judaism holds that a specific oral law (later redacted in the Talmud) explains the meaning and context of these Biblical laws. In this view the death penalty was rarely used, and exceedingly difficult to carry out.
These laws make it clear that the death penalty was only used in extremely rare cases. Rabbinic law developed a detailed system of checks and balances to make sure that the penalty could only be carried out if there were two witnesses to the crime, if the witnesses then verbally warned the person that they were liable for the death penalty, and that the person then had to acknowledge that he/she was warned, but then went ahead and committed the sin regardless. Further, an individual was not allowed to testify against themselves. As such, the death penalty was effectively legislated out of existence.