Supporters of U.S. President Donald Trump gather in Washington
Police clear the U.S. Capitol Building with tear gas as supporters of U.S. President Donald Trump gather outside, in Washington, U.S. January 6, 2021.

A former Virginia police sergeant who joined Donald Trump's supporters in storming the Capitol on Jan. 6, 2021, could be sentenced to up to eight years in prison on Thursday if a judge agrees with federal prosecutors' recommendation.

A jury in April convicted Thomas Robertson, a former police sergeant for the town of Rocky Mount, Virginia, of six criminal charges, including obstructing an official proceeding and obstruction of justice.

Eight years would be the longest sentence handed down so far in a Capitol riot case, if U.S. District Judge Christopher Cooper agrees with prosecutors, who say that Robertson abused his position of trust as a law enforcement officer.

Earlier this month, a federal judge sentenced Guy Reffitt, an associate of the far-right Three Percenters militia, to seven years and three months in prison.

Thousands of Trump supporters stormed the Capitol on Jan. 6, in an attempt to overturn his election defeat, which Trump falsely claims was the result of fraud.

Robertson's defense attorney is asking for a sentence of no more than 15 months.

He has been in detention since last year, after the judge found he violated court orders and continued to purchase what prosecutors described as an "arsenal" of guns online. FBI agents also found a loaded M4 rifle and a partially assembled pipe bomb at his home during a search.

Robertson's trial featured testimony from Jacob Fracker, who had reported to Robertson on the police force, who entered the Capitol on Jan. 6, 2021, with Robertson where they took selfies together.

Prosecutors said Robertson later destroyed the cell phones they had been using that day.

Fracker, who cooperated with the Justice Department, pleaded guilty to a felony charge of conspiracy in March, and is due to be sentenced on Aug. 16. In exchange for his cooperation, prosecutors are asking the judge to sentence him to six months' probation with a condition of community confinement or home detention.

Prosecutors said Robertson "anticipated violence" on Jan. 6, and he packed gas masks for himself and Fracker, as well as military food rations, water and a large wooden stick.

Robertson "used his law enforcement training to block Metropolitan Police Officers attempting to hold back the mob," federal prosecutor Elizabeth Aloi wrote in the government's sentencing memo.

In a letter to the judge, Robertson said he takes "full responsibility" for his actions on Jan. 6, and said that he was "exposed to lots of pro-Trump, anti-Biden media" while he was passing the time in 2020 with a cancer-stricken friend.

He drank to cope with stress, he said, and fell deep into the "rabbit holes of election conspiracy theories."

However, he denied ever having "any intention to disrupt Congress" and claimed that Fracker actually destroyed the cell phones, and later lied to the FBI and the court about it.