05/14/2014 at 08:00 PM EDT
Actor Jason Patric
scored a victory Wednesday in his legal fight to see his biological son
, Gus, 4.
A California Appellate Court has reversed a lower court's finding that he has no parental rights over the child. The question of whether Patric is the legal father is expected to resume at trial where it left off in February 2013.
The boy's mother, Danielle Schreiber, 41, has alleged that Patric, 47, was merely a sperm donor when they conceived Gus through in vitro fertilization in 2009; he contends he was a willing coparent all along.
A Los Angeles Superior Court judge previously had dismissed the actor's paternity claim because he and ex-girlfriend Schreiber were not married at the time of conception, and found they had no coparenting agreement in place.
Patric and Schreiber, who had dated off and on for about 10 years, split for good in June 2012. He filed a paternity claim shortly thereafter.
The actor has been forbidden by Schreiber, who currently is the sole legal parent, from seeing Gus for more than a year.
"I think this time around, Patric has a good chance of winning parental rights for the simple fact that, for a certain period of time, his ex-girlfriend encouraged Patric to have a relationship with the child and held him out as the father," says L.A. family lawyer Lynn Soodik, who's not involved with the case.
Schreiber's attorney Patrica Glaser tells PEOPLE: "We respectfully disagree with the court of appeal. We are exploring our options and should make a decision shortly. The best interest of the child continues to be our goal. His well being, not publicty, will dictate how we proceed."