A former US Capitol Police officer has been convicted of obstructing an FBI investigation into the January 6, 2021, attack on the Capitol by deleting Facebook messages he sent to a rioter afterward, federal prosecutors say.

A jury found Michael Riley, 51, guilty of a single count of obstruction of justice following his trial in federal court for the District of Columbia, a US Attorney’s Office spokesman said on Friday.

Jurors deadlocked on a second obstruction of justice count against Riley, prosecutors said. US District Judge Amy Berman Jackson declared a mistrial on that charge.

The obstruction of justice conviction carries a statutory maximum of 20 years in prison, although federal sentencing guidelines typically call for less time behind bars.

“Michael Riley never obstructed any grand jury proceeding, nor did he attempt or intend to do so,” his attorney, Christopher Macchiaroli, said in a statement.

Mr Macchiaroli said Riley intended to raise legal challenges to the verdict.

Prosecutors say Riley was not on duty at the Capitol Building in Washington on January 6 but became aware of the events there.

Seeing that a Facebook “friend” was involved, he messaged the man, telling him to take down what could be seen as incriminating posts.

Riley deleted the messages after learning the FBI had been in contact with his Facebook friend. The two men had not met in person.

Supporters of Donald Trump stormed the Capitol on January 6, 2021, after he delivered a fiery speech at a rally near the White House that falsely claimed his defeat in the 2020 presidential election by Joe Biden was the result of fraud.

– AAP