Prince George's County Council members yesterday sat through a five-hour presentation billed as an effort to help them decide the bitterly contested route of the county's Metro Green Line. But it was clear that at least six of the nine council members had made up their minds where the route should end and were using the session as a way to lobby colleagues undecided on one of two end stations.

"This is mainly for the new members. Unless I hear something new I'm going to stay the course," said council chairman Frank Casula, who along with two other members has voted in the past for an end station near the Rosecroft Raceway.

"I'm trying to listen, but I don't hear anything I didn't already know," said council member JoAnn Bell, a newly elected member who campaigned on a promise to support a line ending at Branch Avenue and Auth Way, and who is supported by at least two of her colleagues.

The Metro board voted in November to stop the line at Rosecroft, ending 15 years of controversy--or so some people hoped. But in December, Bell and council member Sue V. Mills introduced a measure instructing the board to move the stop to Branch Avenue. That measure was the subject of yesterday's session.

The Metro board is the only authority that can legally change the route, according to Metro legal advisers who said in November that their decision would be final. But as a practical matter, county officials said yesterday, the board has never gone against the wishes of the local government, which can vote to withhold its share of Metro funding.

Branch Avenue supporters say their line is the "original route" and the one expected by the voters when they approved funding for Metro in 1968.

Rosecroft supporters argue, meanwhile, that their line would cost about $100 million less to build and would serve the entire south county more equitably.

The Metro board voted to support the Branch Avenue stop in 1968. In 1978, the council voted to endorse both the Rosecroft and Branch Avenue lines, but selected Rosecroft when forced to choose one route. Two years later, a local businessman filed a lawsuit that is still pending against the Rosecroft decision, saying the change had hurt his business plans and had been improperly advertised.

"It's a tough one," said Anthony Cicoria, one of the few apparently uncommitted votes on the council.