Ruto and co-defendant Joshua Arap Sang entered not guilty pleas Sept. 10 to charges of crimes against humanity.
Testimony began Tuesday with a witness identified as 536, though members of the media identified her by name after her court appearance, Capitalfm.co.ke reported Thursday.
ICC Trial Chamber V Presiding Judge Chile Eboe-Osuju ruled the witness should be allowed to continue giving testimony in private to protect her identity, the news website said.
Lawyers for Ruto and Sang argued against the ruling, saying witnesses should give testimony in public to allow people to see through what they called obvious lies.
Eboe-Osuji said anyone who revealed the identity of a protected witness could be found in contempt of court, the BBC reported.
Ruto and Sang are accused of crimes against humanity, including murder, deportation or forcible transfer of population and persecution, allegedly committed in Kenya following the 2007 election. Some 1,000 people died in the violence.
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