Liberia's jailed ex-President Charles Taylor is due to begin his appeal at a UN-backed special court in The Hague.
Last May, the court sentenced him to 50 years in prison for aiding and abetting rebels in neighbouring Sierra Leone during the 1991-2002 civil war.
Defence lawyers have called the verdict a "miscarriage of justice" and ask for the conviction to be squashed.
Meanwhile Taylor, 64, has reportedly written to MPs demanding a presidential pension of $25,000 (£15,600).
Describing the withholding of his state presidential pension as a "mammoth injustice", Taylor is quoted in the letter as saying that he is entitled to consular access and diplomatic services at The Hague, but he has been "denied that right".
Taylor became the first former head of state to be convicted of war crimes by an international court since the Nuremberg trials of Nazis after World War II.
Throughout his trial, the former Liberian leader, who was arrested in 2006, maintained his innocence.
'Heinous crimes'
The court was set up in 2002 to try those who bore the greatest responsibility for the war in Sierra Leone in which some 50,000 people were killed.
• 1991: RUF rebellion starts in Sierra Leone
• 1997: Elected president after a 1995 peace deal
• 1999: Liberia's Lurd rebels start an insurrection to oust Taylor
• June 2003: Arrest warrant issued; two months later he steps down and goes into exile to Nigeria
• March 2006: Arrested after a failed escape bid and sent to Sierra Leone
• June 2007: His trial opens - hosted in The Hague for security reasons
• April 2012: Convicted of aiding and abetting the commission of war crimes
• May 2012: Sentenced to 50 years in jail
• June 2012: His lawyers say he will appeal against his conviction
It found Taylor guilty on 11 counts of war crimes, relating to atrocities that included rape and murder, and described by one of the judges as "some of the most heinous crimes in human history".
In return for so-called blood diamonds, Taylor provided arms and both logistical and moral support to Sierra Leone's Revolutionary United Front (RUF) rebels - prolonging the conflict and the suffering of the people of Sierra Leone.
His lawyers have filed 42 grounds of appeal, arguing that the trial chamber's findings were based on "uncorroborated hearsay evidence".
"The colossal judgment, over 2,500 pages in length, is plagued throughout by internal inconsistencies, misstatements of evidence and conflicting findings," his lawyer Morris Anyah said in court papers quoted by the AFP news agency.
Prosecutors, meanwhile, are expected to argue that the court made a mistake by only convicting Taylor of aiding and abetting the RUF and its allies, the Armed Forces Revolutionary Council.
"The Trial Chamber erred in law and in fact by failing to convict Mr Taylor for ordering crimes committed by RUF/AFRC forces who were implementing his instructions," the prosecution said in court papers.
Taylor started Liberia's civil war as a warlord in 1989, and was elected president in 1997. He governed for six years before being forced into exile in southern Nigeria. He was arrested in 2006 while trying to flee Nigeria.
The trial was moved to the Netherlands due to concerns that the case might spark fresh instability in Sierra Leone and Liberia.
