Security forces in Egypt targeted activists and critics of the military regime in the run-up to the fifth anniversary of the 2011 revolution on Monday.
Dr Taher Mokhtar is one of many seized from their homes or the streets by police.
He is a leading activist in the Egyptian Doctor’s Union and a revolutionary socialist.
Taher was a well-known figure on doctors’ picket lines during their national strikes in 2011, 2012 and 2014.
He is also a campaigner for prisoners’ rights to health care and treatment in custody.
Since General el-Sisi’s military coup of 2013, thousands of political activists have been imprisoned and hundreds have been sentenced to death.
Many others face long prison sentences, or months and years in prison without trial.
Taher faces charges of “possessing publications calling for the overthrow of the regime” following his arrest on 14 January along with two of his flatmates.
He has also been accused of calling for protests on the uprising’s coming anniversary.
Lawyer Malek Adly said that Taher has been accused of participating in violent clashes following “the January events”.
The doctor answered his interrogators that he indeed participated in the January Revolution and that it was not a crime.
In an act of solidarity posted with the #I_ participated_in_January_Revolution hashtag on Twitter and Facebook.
They stressed that taking part in the 2011 protests that led to the removal of former president Hosni Mubarak was not a crime.
Within days the hashtag had come to dominate social media.
Tens of thousands of people have shown solidarity with Taher and recalled their pride at having participated in the revolution.
Taher has been a leading voice campaigning for prisoners’ rights and was prominent in the campaign for justice for Khaled Said.
Khaled was the young Alexandrian activist whose brutal death at the hands of the police sparked the protests which led to the 2011 revolution.
He has spoken out against the repression of opposition across the political spectrum.
A group of public figures have also signed a press statement entitled “I participated in the January revolution”.
This condemns the detention of Taher and expresses the signatories’ pride in having participated in the revolution.
The statement denounced turning participation in the revolt into an “official charge” in public prosecution investigations.
“What we have said repeatedly and was later proven by the regime, its laws and official bodies is that you are either with the regime or with the January revolution.”
The crackdown has sparked international anger—sign a solidarity statement at bit.ly/239ZJLw