Capital punishment: Inhumane aberration or necessary deterrent?

Australian death-row prisoners Myuran Sukumaran (r) and Andrew Chan (l) stand in front of their cell during an Indonesian Independence Day celebration at Kerobokan prison in Bali, Indonesia in 2011.

(CNN)As Australia appeals for clemency for two of its citizens awaiting execution in Indonesia for drug trafficking, the spotlight is once again focused on the practice of state-sanctioned killing as punishment for a range of crimes.

So what are the key facts, figures and arguments surrounding the death penalty?
Is the use of capital punishment increasing or declining? What would account for these trends?
Despite a global trend towards abolition, in 2013, the latest data available from Amnesty International, executions rose by almost 15% over the previous year. The spike of recorded, verifiable executions, according to the organization, were perpetrated by an "isolated group of entrenched executioners, mainly Iraq and Iran."
    Excluding China, for which figures are not known, Amnesty reveals that 778 confirmed executions were carried out in 2013.
    However, despite an increase in numbers of executions as a whole, there is a general trend towards abolition, with an increasing number of territories and countries across the globe moving toward moratorium or abolition.
    Worst offenders: Which countries execute the most people?
    Amnesty reports that 22 countries conducted executions during 2013, one more than in the previous year. Four countries -- Indonesia, Kuwait, Nigeria and Vietnam -- resumed executions after moratoriums were lifted there.
    China, which is believed to execute more prisoners each year than the rest of the world combined, does not release figures on its executions and thus reliable figures are hard to come by.
    While concrete data is difficult to obtain in many countries, Amnesty says that almost 80% of all known executions (which excludes China's figures) worldwide were recorded in Iran, Iraq and Saudi Arabia.
    Earlier this year, Egypt condemned 183 defendants to death in a mass sentencing, triggering international opprobrium and calling the Egyptian justice system into sharp relief.
    The United States, which executed 39 people in 2013, is the only G7 country, and the only one of 56 member states of the Organization for Security and Cooperation in Europe, to still use capital punishment.
    Which countries have abolished the death penalty?
    More than two thirds of countries have struck capital punishment from their statutes, or at least for all practical purposes. In 2013 no executions were recorded in Europe and Central Asia, and the U.S. was the only country in the Americas to execute people in 2013. Only three ASEAN nations -- including Indonesia -- carried out executions that year. Of the G8, only two -- the United States and Japan -- executed prisoners.
    When do prisoners find out about their impeding execution?
    This differs from country to country, ranging from an execution date -- pending appeals -- set at sentencing in the United States, to inmates unaware of their scheduled death until just a few days or hours before being killed, as is the case the Bali 9 as they await their fates in Indonesia.
    How are prisoners executed?
    Methods of execution range from lethal injection -- first adopted in the United States in 1977 -- to gassing, hanging, death by firing squad, electrocution and beheading -- Saudi Arabia still publicly executes prisoners by decapitating them with a sword.
    How accurate are figures on the death penalty?
    Amnesty says: "In some countries, it is not possible to obtain reliable data because governments do not make figures for death sentences and executions available, while others actively conceal death penalty proceedings. In countries affected by conflict it is often not possible to obtain sufficient information to confirm whether any executions have taken place."
    How are cases of foreign nationals sentenced to death treated?
    Foreigners on trial in countries with the death penalty can be at a disadvantage due to linguistic difficulties and an unfamiliarity with the country's legal system; however, those arrested abroad are granted consular assistance under the Vienna Convention on Consular Relations (VCCR).
    Diplomatic solutions occasionally see prisoners repatriated to serve out sentences -- in lieu of execution -- in their home countries.
    Indeed, the VCCR has been cited in diplomatic attempts to repatriate death row citizens -- Mexico invoked the United States' failure to abide by the convention as reason to repatriate 54 Mexican nationals in death row in the U.S.
    However, foreigners often fall foul of some country's laws -- drug trafficking cases are often headline-grabbers -- and in some high profile cases, despite diplomatic appeals, politicians choose to go ahead with executions in a bid to appear unwavering in the face of serious crime.
    What are the arguments for and against the practice?
    Advocates say it is a powerful deterrent against serious crime, while others point to the problems -- and cost -- of keeping violent offenders in general prison populations. In many countries, justice is seen as served due to the satisfaction of the victims or their families in seeing perpetrators put to death.
    Opponents cite the arbitrariness of the death penalty, the fallibility of juries and the problems associated with wrongful conviction. In the United States, there are also claims that there are racial disparities and that African-Americans are overrepresented on Death Row.