Gardaí left a detainee masked with a spit hood for more than five hours.
It is one of the revelations in a report by the Policing Authority on the force's use of special powers during the pandemic.
Officers used the hoods 86 times in the space of 15 weeks, removing them in under 20 minutes or less in 85% of cases.
The Garda Commissioner has said their use is a last resort.
But Colm O'Gorman from Amnesty Ireland says the companies which make them have warned they are not designed to stop the spread of Covid-19.
“It seems to us that the use of a spit hood for a period of five hours, to be very difficult to see how that is either necessary or proportionate,” he said.
“And that is a concern.
“There are now suggestions that spit hoods may not protect against aerosol contamination of Covid-19.
“And if you think about circumstances in which spit hoods are used, if there’s a struggle to place a hood on somebody, et cetera.”