A Canadian woman has been sentenced to nearly 22 years in prison in Washington over the mailing of a threatening letter containing the poison ricin to then-US president Donald Trump at the White House.

Pascale Ferrier, 56, had pleaded guilty to violating biological weapons prohibitions in letters sent to Mr Trump and to police officials in Texas, where she had been jailed in 2019 after refusing to leave a park area as it closed.

Her defence lawyer Eugene Ohm said Ferrier has no criminal record prior that and is an “inordinately intelligent” French immigrant who had earned a master’s degree in engineering and raised two children as a single parent.

But in September 2020, prosecutors said Ferrier made the ricin, a potentially deadly poison, then mailed it to Mr Trump with a letter that referred to him as “The Ugly Tyrant Clown” and read in part: “If it doesn’t work, I’ll find better recipe for another poison, or I might use my gun when I’ll be able to come. Enjoy! FREE REBEL SPIRIT.”

The letter from Ferrier, which also told Mr Trump to “give up and remove your application for this election”, was intercepted at a mail sorting facility in September 2020, before it could reach the White House.

She was arrested trying to enter a border crossing in Buffalo, New York, carrying a gun, a knife and hundreds of rounds of ammunition, authorities said.

Investigators also found eight similar letters to Texas officials.

In a winding speech, Ferrier told the judge that she considers herself a “peaceful and genuinely kind person”, but gets angry about problems such as unfairness, abuses of power and “stupid rules”.

She spoke about feeling like she had done little to support her values while raising her children, and considered herself to be an “activist” rather than a “terrorist”.

“I want to find peaceful means to achieve my goals,” she said.

US District Judge Dabney L Friedrich handed down the 262-month sentence outlined in a plea agreement with prosecutors, which also requires Ferrier to leave the country once she is released and be under supervised release for life if she ever returns to the US.

The judge noted a “real disconnect” between the Canadian grandmother who has worked towards another degree while behind bars and the crimes Ferrier pleaded guilty to.

“That isn’t really activism, that’s productive,” she said.

Prosecutor Michael Friedman said the sentence was an “appropriately harsh punishment” that sends a clear message.

“There is absolutely no place for politically motivated violence in the United States of America,” he said.