CINCINNATI — An Ohio man who plotted to attack the US Capitol during President Obama’s 2015 State of the Union address kept trying from behind bars to urge others to violence in support of the Islamic State group, federal authorities say.

Prosecutors described Christopher Cornell’s jail activities in a sentencing memorandum filed this week ahead of a Dec. 5 sentencing hearing. They want a judge to sentence him to 30 years in prison after he pleaded guilty earlier this year to three charges.

‘‘This case is unusual in the amount of post-arrest conduct and misconduct by the defendant . . . his persistence in trying to incite violence and his efforts to obstruct justice through witness intimidation,’’ said the filing by US Attorney Benjamin C. Glassman’s office.

Associated Press