BOSTON — More than five years after a Boston boy named Giovanni disappeared during a weekend visit with his father, charges against the man could be dismissed because of mental illness. The boy’s father, Ernesto Gonzalez, was charged with parental kidnapping and misleading investigators, and has been in jail ever since. Giovanni has never been found.

Gonzalez’s lawyer, Russell Sobelman, said he plans to argue for dismissal during a hearing Tuesday in Salem Superior Court. Giovanni’s mother believes her son is still alive and being hidden somewhere by friends of Gonzalez.

Under a state law, defendants who have been declared incompetent to stand trial can move for dismissal if they have served at least half the maximum sentence they would have received if convicted.

Gonzalez has been in jail since August 2008, so he has already served more than half of the 10-year maximum sentence he faced. He was declared incompetent last month after a judge reviewed medical reports that said Gonzalez suffers from a serious mental illness and is unable to assist in his defense.

Giovanni’s mother, Daisy Colon, said she believes Gonzalez has been playing the system.

“From Day One, it’s been back and forth, back and forth. He’s competent one day, then the next, he’s not,” she said.

Sobelman said that even if the charges are dismissed, Gonzalez will not be released from jail anytime soon because of two other pending criminal cases in alleged attacks on a fellow inmate and a guard. He has also been ordered confined to Bridgewater State Hospital under a civil commitment petition filed by psychiatrists there, Sobelman said.

Carrie Kimball Monahan, a spokeswoman for Essex District Attorney Jonathan Blodgett, said that under the law, prosecutors cannot oppose a move to dismiss the parental kidnapping and misleading police charges because the “clock has run out on those charges.” She said prosecutors would oppose any attempt to dismiss the unrelated assault charges against Gonzalez.