President Donald Trump has suggested a man pushed over by police during protests in the US city of Buffalo last week was trying to “scan police communications in order to black out the equipment”.
But is this even possible?
Footage of 75-year-old Martin Gugino shows him approaching police lines holding up what appears to be a mobile phone.
One of the police officers then pushes Mr Gugino over, who was later taken to hospital. He left hospital today but was not well enough to comment.
From the clip, it’s not possible to tell what he was doing with the phone. We’ve seen no evidence to suggest he was trying to scan police devices. It is also not clear how police equipment could be interfered with in this way.
There are plenty of apps claiming to be able to listen into police audio that have been popular during the recent wave of protests in the United States.
But these apps wouldn’t allow you to interfere with a police device – or to “black out police equipment” as the president suggested.
Buffalo police say their dispatch channels are not encrypted, and there are even websites that broadcast police calls.
If you were attempting to jam police radio signals, you wouldn’t need to be physically close to an officer.
However, most modern radio systems used by emergency services have defences against such jamming, says Professor Alan Woodward, a cyber security expert at Surrey University.
“In any event, even if you were attempting to scan police radios in order to jam them using a mobile phone, which is what the man appeared to be holding, this is not the equipment you would use. You would need much more sophisticated scanning equipment.
“In terms of interfering with police communications frequencies, mobile phones simply don’t have components that work at those frequencies,” he adds.
How has Mr Gugino responded?
In a statement to the Washington Post, a lawyer for Mr Gugino said his family was at a loss as to why Mr Trump had made “a dark, dangerous and untrue accusation” against him.
“Martin has always been a peaceful protester because he cares about today’s society,” Kelly Zarcone said. “No one from law enforcement has suggested otherwise,” she added.
The post gave no evidence of a link between Mr Gugino and antifa, a loose affiliation of anti-fascist and mostly left-wing activists which Mr Trump has blamed, without providing proof, for acts of violence during the protests.
Twitter, which has censored previous tweets by the president, said this tweet did not violate its rules.
The claim appeared to first gain traction from a widely shared conservative blog post published on 6 June also claiming that antifa activists use this technique to track police movements or “black out” communication.
These then appeared on conservative outlet One America News Network (OANN) before ending up on the president’s social media profiles.
Many people responded angrily to the president’s suggestion the incident which led to Mr Gugino’s injury was “a set up” and accused him of promoting a conspiracy theory.