A 25-year-old American woman faces up to 20 years behind bars in Zimbabwe after being charged with subversion for allegedly mocking the country’s president on Twitter, Associated Press reports. Martha O’Donovan made her first court appearance on Saturday after police took her from her home in the capital, Harare, on Friday. Accused of calling 93-year-old President Robert Mugabe a “sick man” in a Twitter post that included a photo of the president with a catheter, O’Donovan has called the charges “baseless and malicious.” O’Donovan, a graduate of New York University who’d been working with social media outlet Magamba TV, is also charged with undermining the authority of or insulting the president. The arrest comes after Mugabe’s appointment of a cybersecurity minister last month set off alarm bells among activists. “This arrest marks the start of a sinister new chapter in the Zimbabwean government’s clampdown on freedom of speech, and the new battleground is social media,” Amnesty International’s deputy regional director, Muleya Mwananyanda, said of the charges against O’Donovan.