Palestinians flee Israeli tanks in Khan Younis, southern Gaza, 26 January 2024 (AFP)
Editor's note: This is one of four explainers about international law. The series includes an overview, as well as separate pieces about crimes against humanity and war crimes.
In December 2023, South Africa accused Israel before the International Court of Justice (ICJ) for its war on Gaza. More than a year later, and the ICJ, the world's highest court, is still hearing the case.
In the meantime, international human rights groups, scholars, and UN experts have come up with their own judgments that genocide has been committed in the Palestinian enclave, where at least 48,440 people were killed between 7 October 2023 and 5 March 2025, according to the Palestinian health ministry.
But what is "genocide"? And how does international law define and prosecute this most serious of crimes?
What is the definition of genocide?
The definition of genocide focuses on the destruction, or intent to destroy, in whole or in part, a national, ethnic, racial, or religious group. It is one of the most serious international crimes, alongside crimes against humanity, and war crimes. They are collectively known as “core international crimes” or “atrocity crimes”.
);display:none;">Genocide is widely recognised as “the crime of all crimes”: it doesn't need to be part of a war between countries, and can exist, for example, as part of an internal domestic policy against an identifiable group.
What makes genocide different?
What differentiates crimes from each other is their core elements: the mens rea (the mental element of intent or knowledge); and the actus reus (the prohibited acts themselves).
An Israeli tank overlooks Palestinians fleeing Khan Younis in the southern Gaza Strip on 26 January 2024 (AFP)
For genocide, the intention is specific: to destroy, in whole or in part, a national, ethnic, racial, or religious group. Other actions that lead up to genocide are also prohibited and considered substantive crimes under the 1948 Genocide Convention - more on that below.
Which courts hear cases of genocide?
In general, national courts can prosecute allegations of genocide, regardless of where the act was committed or the nationality of the defendant or victims.
But, the key international judiciaries usually associated with genocide are the International Court of Justice (ICJ), founded in 1945, and the ICC (founded in 2002). Both sit in The Hague in the Netherlands.
The ICJ intervenes in disputes between states, not least if one country alleges that another has committed genocide, as in the case that South Africa brought against Israel.
The ICC only considers cases against individuals - but only when national judiciaries are unable or unwilling to do so.
What is the etymology of the word ‘genocide’?
The word genocide is derived from “genos”, which is the Greek word for “race or tribe”; and “cide” the Latin suffix indicating "to kill". It is defined in the Oxford English Dictionary as "the deliberate killing of a very large number of people from a particular ethnic group or nation".
Who defined the word genocide?
Raphael Lemkin, a Jewish Polish lawyer, devised the word in 1944, following the Holocaust perpetrated by Nazi Germany, using it to describe the systemic murder of six million European Jews and other groups.
Jewish women and children arrive at the Auschwitz extermination camp in occupied Poland in 1943 (AFP)
") rgba(220, 220, 220, 0.5); top: -15px; left: 0px;">The word first appeared in Lemkin’s book Axis Rule in Occupied Europe as the heading for Chapter IX: “Genocide - A new term and new conception for destruction of nations.” Taking the example of Nazi rule over occupied Europe, he examines the various forms of genocide and how it can be applied.
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") rgba(220, 220, 220, 0.5); top: -15px; left: 0px;">Genocide, Lemkin suggested, was not just about the act itself, but also what came before that, including the incitement and conspiracy to commit genocide across many human activities.
Raphael Lemkin, the Jewish Polish lawyer, when invented the word “genocide” in response to the Holocaust and other atrocities of World War Two (Creative Commons)
Nor does genocide necessarily mean the immediate destruction of a nation: rather it's about a coordinated plan of diverse actions to destroy its foundations. Here's what Lemkin wrote:
“The objectives of such a plan would be disintegration of the political and social institutions, of culture, language, national feelings, religion, and the economic existence of national groups, and the destruction of the personal security, liberty, health, dignity, and even the lives of the individuals belonging to such groups. Genocide is directed against the national group as an entity, and the actions involved are directed against individuals, not in their individual capacity, but as members of the national group.”
When was the legal definition of genocide introduced?
Genocide was not officially adopted by the time of the post-World War Two trials that began in 1946 in Nuremberg and Tokyo. Instead, defendants were accused of crimes against peace, war crimes, and crimes against humanity. At Nuremberg, for example, Nazi war criminals faced Holocaust-related charges including extermination and persecution on political, racial, or religious grounds.
Genocide was first mentioned legally in the Genocide Convention of 1948 (or the Convention on the Prevention and Punishment of the Crime of Genocide to give its full title). In Article II it states that "genocide means any of the following acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group". That might include
- Killing members of the group
- Causing serious bodily or mental harm to members of the group
- Deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part
- Imposing measures intended to prevent births within the group
- Forcibly transferring children of the group to another group
This is followed by Article III, which also prohibits:
- Conspiracy to commit genocide
- Direct and public incitement to commit genocide
- Any attempt to commit genocide
- Complicity in genocide
These articles were hugely important: they would go on to influence and form part of subsequent tribunals for Yugoslavia, Rwanda, the Rome Statute, and ultimately the ICC.
Who rules on cases of genocide?
The ICC or any ad hoc tribunal (a temporary court created for a specific case, as with Rwanda and Yugoslavia) can decide whether individuals are guilty of genocide. Likewise, the ICJ can rule whether a state has violated the Genocide Convention.
National courts can also prosecute individuals for genocide and hold them accountable: the case does not need to be within their borders or involve any of their citizens.
Yazidis from northern Iraq cross the Tigris river into Syria to escape atrocities committed by Islamic State in August 2014 (AFP)
") rgba(220, 220, 220, 0.5); top: -15px; left: 0px;">This happened, for example, in Germany in September 1997, when courts prosecuted individuals for genocide committed during the Bosnian War. Eventually, the Higher Regional Court of Dusseldorf convicted Nikola Jorgic, a Bosnian Serb paramilitary leader, of genocide and sentenced him to four life terms.
") rgba(220, 220, 220, 0.5); top: -15px; left: 0px;">Likewise, in November 2021, the Higher Regional Court in Frankfurt convicted Taha Al J for genocide against the Yazidis in Iraq.
How is genocide proved?
Three criteria must be fulfilled to prove genocide:
- The targeted group must have a shared characteristic as identified in the Genocide Convention: it could be national, ethnic, racial and/or religious
- At least one of the acts of genocide mentioned in Article II must have been committed
- There must have been a specific intention to commit the act or acts. This can be proved directly through evidence such as statements or comments; or indirectly, for example through circumstantial evidence, a pattern of conduct, the systemic nature of the acts, and the extent of the harm.
Only courts have the legal power to decide if genocide has been committed. But the terms of the crime are included in publicly available treaties, statutes, and rulings. This allows organisations and others to make their own assessments and give opinions.
For example, in December 2024, Amnesty International concluded that Israel had committed genocide during its war on Gaza.
Amnesty’s secretary-general Agnes Callamard told Middle East Eye that Israel had argued that it was pursuing a legitimate military objective by trying to get rid of Hamas.
“However, those military objectives do not justify or excuse genocidal intent,” she said. “Genocidal intent can coexist with military objectives.”
What are some older examples of genocide?
Russian soldiers in the village of Sheykhalan in 1915 during the Armenian genocide (Creative Commons)
") rgba(220, 220, 220, 0.5); top: -15px; left: 0px;">Several historical atrocities which pre-date 1948 have retrospectively been recognised by scholars, governments, and international institutions as acts of genocide. They include:
The Ottoman Empire (1915–1917, now Turkey): The Armenian Genocide resulted in the deaths of around 1.5m Armenians, who were systematically exterminated through mass executions, forced deportations, and starvation. Despite being disputed by Turkey, the catastrophe has now been recognised as genocide by much of the world, including the US in late 2019.
German South West Africa (1904-1908, now Namibia): Tens of thousands of the Herero and Nama were subject to genocide carried out by German colonial forces.
The Congo Free State (1885-1908, now the DRC): An estimated six to 10 million Congolese were killed amid the atrocities committed under the colonial rule of King Leopold II of Belgium.
The Americas (late 15th century onwards): The arrival of European colonial powers in North and South America led to forced displacements, massacres, deliberate exposure to disease, and cultural destruction, causing the deaths of tens of millions of Indigenous peoples.
Has anyone been convicted of genocide?
Yes, there have been several examples, especially in the late 20th and early 21st centuries. Jean Kambanda, the one-time prime minister of Rwanda, was convicted by the International Criminal Tribunal for Rwanda (ICTR) in 1998 after pleading guilty to genocide and crimes against humanity. Sentenced to life imprisonment, he was the first head of state to be convicted of the crime.
Rwandan refugees cross Rusumo border to Tanzania from Rwanda in May 1994 amid the genocide (Reuters)
") rgba(220, 220, 220, 0.5); top: -15px; left: 0px;">In 2016, Radovan Karadzic, the former president of Republika Srpska, a Bosnian Serb entity, was found guilty by the International Criminal Tribunal for the Former Yugoslavia (ICTY) of genocide, crimes against humanity and war crimes committed during the Bosnian War.
In 2018, the Extraordinary Chambers in the Courts of Cambodia (ECCC) convicted senior Khmer Rouge leaders, Nuon Chea and Khieu Samphan, of genocide against the Cham Muslim and Vietnamese minorities from 1975 to 1979.
Is genocide the same as ethnic cleansing?
No. Ethnic cleansing is not defined as a crime itself, although its underlying sense reflects that of genocide.
The term ethnic cleansing emerged during the Yugoslav wars of the 1990s. It describes the forced displacement of an indigenous national, ethnic, racial, or religious group with the intent of making the area ethnically homogenous.
The phrase became better known in February 2025 after US President Donald Trump advocated removing Palestinians from Gaza. Ethnic cleansing is often mentioned in discussions about serious international crimes. And, while not defined as a crime itself, the underlying intent of “ethnic cleansing” is reflected in Article 49 of Geneva Convention IV, which references “forced transfers” and” forced deportations” as war crimes.
Is genocide like crimes against humanity?
Genocide and crimes against humanity are separate crimes, although they may have overlapping elements. Unlike genocide, there is no treaty dedicated to crimes against humanity.
The International Law Commission, the UN body that develops international law, is currently working on a draft convention for crimes against humanity.
