The International Criminal Court`s prosecution of Kenyan President Uhuru Kenyatta has stumbled mainly on the vulnerability of witnesses, allegedly bribed, intimidated or exposed as liars.
The office of ICC prosecutor Fatou Bensouda has repeatedly said that witnesses were being intimidated in Kenyatta`s case, as well as that of his deputy, William Ruto, whose trial finally began in September 2013.
Both men are charged with crimes against humanity for their alleged role in masterminding post-election violence in 2007 and 2008 that left 1,200 people dead and 600,000 displaced. They deny the charges.
Already in February 2013, the prosecution admitted it was dealing with "the unique security challenges and unprecedented level of witness interference in this case".
The defence has rejected the accusations.
When former foes Kenyatta, the son of Kenya`s first president and independence hero Jomo Kenyatta, and Ruto won their mandates as allies in an election in March last year, the pressure increased and the delays multiplied.
On March 11, Bensouda said she was dropping charges against top civil servant Francis Muthaura, a first since the ICC was set up in 2002.
She said that a key witness had withdrawn, other witnesses had died and that Kenyan authorities were not cooperating.
At least seven witnesses have withdrawn in the Kenyatta case alone since the beginning of 2013, according to the International Justice Monitor. A third of the witnesses in Ruto`s case have also dropped out, said a judicial source who asked not to be named.
Some refused to testify citing concerns for their safety. Others withdrew their testimony, sometimes turning it against the prosecutor, accused of encouraging them to make false statements.In May 2013, Bensouda informed judges of "reports received from prosecution witnesses that they have been targeted by (Kenyan government) officials seeking to influence their testimony".
In August last year, the ICC issued an arrest warrant against former Kenyan journalist Walter Barasa, suspected of bribing or corrupting witnesses in Ruto`s trial, the first such warrant in the court`s history.
The identity of witnesses is theoretically secret as they are only identified by numbers. But their identities are told to defence lawyers so that they can prepare for their testimony.
A woman known as "Witness P0536" who testified against Ruto in September 2013, her face pixellated and voice distorted, had her identity revealed by Kenyan media and bloggers.
"Now that a witness has been identified it will be difficult to assure others that they are their family members will be safe," said the Kenyan Human Rights Commission, an independent NGO.
"Witnesses are bound to feel that their family and their extended family may be in danger and might want to withdraw."
Richard Dicker, director of Human Rights Watch`s international justice programme, said that if the case against Kenyatta collapses, there will be "imperative" lessons to be learned.
"That entails what is necessary in terms of witness protection in instances when senior government officials are charged and the need to improve this witness protection," he told AFP.
"There is also a need to conduct a deeper, stronger investigation that relies on different sources beyond witness` testimony," including forensics, Dicker said.