People taking bottles of water into courts are being ordered to take sips to prove it is not acid in a security crackdown.
The checks are designed to stop would-be attackers from throwing acid at judges, jurors or witnesses.
The measure applies to anyone bringing a drink into court buildings, including lawyers, journalists and staff.
It began at Cardiff Crown Court this week and is being rolled out across the country.
It has led to longer queues as security staff checked unsealed bottles.
The Ministry of Justice (MoJ) said the checks were part of "enhanced security measures" being brought in across the court estate.
A security guard at Cardiff Crown Court said: "It would be very easy to conceal in a plastic bottle so when people come through and into the court we have to ask them to take a sip of their drink to prove it is not acid.
"One family came into the court with a little boy who looked about three of four years old and was carrying a child's beaker.
"We had to ask the parents to take a sip of the drink to prove it wasn't acid, but it was the little boy who took the sip of the drink so we could allow them into the court."
One regular worker added: "I was having my bag searched while going into court last week and the guard held out my water bottle and asked me to take a sip to prove it's not acid.
"I thought they were joking. I asked 'Are you serious? I've been coming here every day'.
"But they wouldn't let me carry on until I took a sip so I didn't have much choice."
A spokesman for HM Courts & Tribunals Service - part of the MoJ - said: "We take the safety and security of court users and staff extremely seriously, which is why we're bringing in enhanced safety measures across the court estate.
"We keep our security procedures under constant review, and will always take action where appropriate."