Former US special counsel Robert Mueller has made a rare public intervention to defend his indictment of former Trump adviser Roger Stone.
Stone was found guilty on charges linked to an investigation led by Mr Mueller that found Russia tried to boost the Trump 2016 election campaign.
President Donald Trump commuted Stone's 40-month jail sentence on Friday saying he was the victim of a "witch-hunt".
In the Washington Post, Mr Mueller said Stone was rightly a convicted felon .
Stone was convicted of obstruction, witness tampering and lying to Congress.
The president's move - sparing Stone from jail but not a pardon - came just after a court denied Stone's request to delay the start date of his prison term.
Leading Democrats and a few Republicans have condemned Mr Trump's decision, saying it undermined the justice system.
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The White House said that Department of Justice prosecutors under Mr Mueller only charged Stone out of frustration after failing to prove the "fantasy" that the Trump campaign had colluded with the Kremlin.
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Mr Mueller writes that he felt compelled to respond to claims that his investigation had been illegitimate, his motives improper, and Stone a victim