Giusti was arrested Wednesday afternoon for threatening Speaker of the House Nancy Pelosi over recent healthcare legislation.
"Greg frequently gets in with a group of people that have really radical ideas and that are not consistent with myself or the rest of the family, which gets him into problems," Eleanor Giusti said. "I say Fox News, or all of those that are really radical, and he, that's where he comes from."
Giusti, 48, has a long history of encounters with law enforcement.
In 2004, Giusti was convicted of criminal threats. The San Mateo District Attorney's office says he was trying to evade the fare on a Caltrain, and when the conductor tried to kick him off, Giusti started yelling and threatening the conductor's life. As a result, Giusti was sentenced to one year in county jail and three years supervised probation. He was also ordered to undergo mental health counseling.
There is also a lawsuit filed in February by Hamilton Square Baptist Church in San Francisco. It says, "Giusti has engaged in and continues to engage in a campaign of harassment" against people at the church.
Giusti also has a record of skipping out on his BART fares and causing disruptions. BART sued him in 1996.
He also has two convictions in San Francisco for welfare fraud and petty theft from 1992.
According to ABC7 legal analyst Dean Johnson, there is a point at which free speech ends and a threat begins.
"Communicating a threat with the intent that it be taken seriously is one of those types of speech that is simply not protected," Johnson said. "Even under state law, as well as the federal law that applies here, there are crimes that are based on threatening another individual, you simply cannot do that."
Eleanor Giusti also told ABC7 she talked to her son earlier in the day -- apparently before the arrest. He asked about his niece and nephew and acted as though nothing was going on.
The FBI told ABC7 Giusti will be booked into San Francisco County Jail to spend the night, before appearing in federal court Thursday morning.
