It happened as the jury informed the judge that it's deadlocked after days of deliberations.
The jury found Mangum guilty of child abuse, but they couldn't agree on a first degree felony arson charge, which could have landed Mangum in jail for seven years.
Mangum made national headlines in 2006 when she accused several Duke Lacrosse players of rape. The players were later exonerated and all charges against them dropped.
She's been on on trial for alleged arson and other charges stemming from a domestic dispute with her former boyfriend in February.
Police said she punched and scratched her then-boyfriend Milton Walker, threw his clothes in a bathtub, and set them on fire. Mangum's three children were in the home at the time, and one of them called 911.
Deciding the case has apparently not been easy for jurors. They told the judge Friday they reached a decision on most of the charges, but were split on the most serious - the arson charge.
During the conversation with Judge Abe Jones Friday, a spectator in the court - former Durham school board member Jackie Wagstaff - was heard uttering "This is ridiculous."
Judge Jones then put her on trial for contempt of court when a bailiff said she was willing to testify that Wagstaff made the comment.
Wagstaff testified that she was having a discussion unrelated to the trial when she made the comment and apologized to the judge, saying she meant no disrespect to his authority.
A second deputy testified that he's had to ask Wagstaff and other Mangum supporters to be quiet at least 2-3 times a day throughout the proceedings.
He said the supporters continue to talk to each other. The deputy said some of the supporters were asked to leave, but he testified the group would argue with him and not accept his request.
Jones found Wagstaff in contempt and sentenced her to jail for 10 days plus a $200 fine.
Mangum was sentenced to time already served and released on bail.
It's unclear if there will be a new trial on her felony arson charge.