Roger Stone wanted to contact Jared Kushner in order to "debrief" the president's son-in-law about hacked emails that were damaging to Hillary Clinton during the 2016 presidential campaign, to train Trump campaign help said in court on Tuesday.

Rick Gates, Donald Trump's deputy campaign chairman and a key cooperator in the special counsel's Russia investigation, appeared on the witness stand in Washington DC.

Stone, a self-confessed "dirty trickster" and Trump adviser, is on the subject of tampering and reluctance.

The testimony spelled out Stone's efforts to at least be seen by the highest ranks of the Trump campaign as a go-between with WikiLeaks, the anti-secretive group that released the damaging emails. Last week, Steve Bannon, who was the chief executive, said the campaign Stone has an "access point" with WikiLeaks.

Gates received a text message from Stone on June 15, 2016, asking for Kushner's contact information. Stone could "debrief" him on the hacked emails, he said. Kushner was a senior adviser to the Trump campaign at the time.

Gates did not say if Stone received Kushner's information. Kushner's attorney did not immediately respond to a message seeking comment.

The prosecution rested their case after recalling a FBI agent who had previously testified about a stone of the earth and then-candidate Trump – including three calls on 14 July 2016, the day has a massive hack of Democratic National Committee servers reported.

Trump was aware of the impending WikiLeaks releases, but pointed out that they were very much involved in trying to figure out what was happening with WikiLeaks.

The president told Mueller's prosecutors in a speech that he had no recollection of any particular conversations about the hacked emails.

Gates told jurors the Trump campaign discussed how they would handle the release of WikiLeaks 'disclosures based both on what they were learning from Stone and WikiLeaks' public statements.

His appearance in the aftermath of the justice department released documents detailing how he describes the campaign in the stolen emails of Democrats to the FBI.

On the booth Tuesday, Gates detailed overhearing a speakerphone conversation in July 2016 between Stone and Paul Manafort, his longtime business associate and the chairman, after WikiLeaks released its first batch of emails and Stone told Manafort "additional information would be forthcoming".

"Mr Manafort thought it would be great," Gates testified.

At the end of July, Gates said, he was with Trump to Trump Tower to LaGuardia Airport when Trump was in the midst of a conversation with Stone, whose voice Gates recognized on the other end of the line.

Defense counsel objected when Gates was asked about it, but it was allowed to testify that Trump indicated that "more information would be coming", presumably related to WikiLeaks.

Gates said that he was not exactly where Stone was telling Trump.

Gates was among the first Trump associates in special counsel Robert Mueller's Russia investigation, alongside Manafort in October 2017. He turned on Manafort in February 2018, pleading guilty to financial crimes arising from the international peer analysis work in Ukraine and to making false statements to investigators.

He has been one of the world's top investigators in the field of investigation and testing at Manafort's 2018 trial and more recently in the case against Greg Craig, a high-powered Washington lawyer who was acquitted in September on allegations that he lied to the justice department about his international lobbying work.

In a sign that Gates' cooperation is nearing an end, prosecutors and defense lawyers have filed a notice on Monday that they are ready for the judge to schedule a date in the middle of the next month.

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