Liberia's former leader lives in exile in Nigeria
A United Nations-backed court in Sierra Leone has begun hearing appeals against their indictments from some of those accused of war crimes.
The case of Liberia's former president, Charles Taylor, accused of supporting rebels in neighbouring Sierra Leone was the first to be heard.
The Special Court for Sierra Leone was set up to try those bearing the greatest responsibility in the atrocities and so far 13 people have been indicted.
An estimated 50,000 people died in the decade-long civil war and many others had their bodies mutilated and limbs hacked off.
A BBC West African analyst says unlike most of those indicted, Mr Taylor continues to live in luxury in a presidential guest house in south-eastern Nigeria.
However, the moment he does try to go anywhere he could be seized and handed over to the court.
SIERRA LEONE SPECIAL COURT
Established by UN and Sierra Leone
Try those most to blame for war crimes
Mandate till 2005
Local and international prosecutors, judges
Funded by UK, US and others
His lawyers are attempting to persuade the court that he should never have been indicted.
The Sierra Leonean barrister representing him started by arguing that Mr Taylor was Liberian head of state at the time when the indictment and arrest warrant were issued and so enjoyed sovereign immunity.
He is also expected to put forward a second motion challenging the indictment on grounds of extra-territoriality, arguing that the court's mandate only applies within Sierra Leone itself.
Meanwhile prosecution lawyers have put forward a motion of their own, arguing that Mr Taylor has no standing to challenge the indictment, since he himself is not present in court.
Of the 12 other appeals to be heard, nine defendants are in custody in Sierra Leone and at least two have died. Several others are also challenging their indictments.
They are expected to argue, among other things, that the court is unconstitutional and that they had been granted amnesty from prosecution as part of the peace agreement
One of the most high profile cases is that of former interior minister Sam Hinga Norman, who during the war ran a pro-government militia, but was arrested in March.
He denies charges of unlawful killings, terrorising the civilian population and using child soldiers.
His lawyer is expected to argue that while using child soldiers may be repugnant it is not a crime under international law.
The militias and rebel forces alike were accused of extreme brutality against civilians during the war which officially ended last year.
The rebels were notorious for hacking off civilians' limbs, mass rape and the recruitment of young children in the war.
Former rebel leader Foday Sankoh died in a hospital in Sierra Leone a few months ago while in the custody of a war crimes court.
Over the next few days the appeal panel of the Special Court will hear arguments from a number of those indicted, and will give its rulings at the end of the session.
The trials proper are not expected to start until early next year.