PHILADELPHIA -- Without a formal state procedure to evaluate whether an injured governor is fit enough to return to work, Gov. Jon S. Corzine's decision on when to return to work will be his alone.

The New Jersey Constitution doesn't address who decides when an incapacitated governor can return to work, though it does give the Legislature and state Supreme Court authority to remove a governor who doesn't return after six months.

Robert Williams, a state constitutional expert and professor at Rutgers-Camden School of Law, called the short-term return question "a little gray." Without a clear procedure, it's apparently simply up to the governor to decide when he's well enough to resume his duties, Williams said.

"It does feel like it's in the hands of the governor," Williams said. "If he sort of sat up in bed and said, 'I'm governor again,' that's probably presumptively it."

The 60-year-old Corzine was seriously injured April 12 when his SUV, being driven by a state trooper at 91 mph, was clipped by a truck and slammed into a guard rail on the Garden State Parkway. Corzine wasn't wearing his seat belt, as required by state law.

He fractured his left thigh and broke 11 ribs, his breastbone and other bones in the crash. He was operated on three times and a metal rod was inserted to stabilize his leg. Corzine had been using a walker to take a few steps in recent days, but he switched to forearm crutches on Saturday, spokesman Anthony Coley said.

While doctors say Corzine has been recovering nicely, he faces a long rehabilitation. It's likely he won't be able to walk without crutches or a cane for six months.

Corzine could leave the hospital as early as Monday, but it's uncertain when he'll return to work as governor.

Since Corzine's accident, Senate President Richard J. Codey has been acting governor, as specified by the state Constitution. But the Constitution doesn't require paperwork to be signed and filed detailing when gubernatorial authority shifts from one person to another, Williams said.

Unlike 42 other states, New Jersey doesn't have an elected lieutenant governor, though it will in January 2010 when a new state law takes effect. After that, the lieutenant governor would take over if the governor is absent or incapacitated.

Codey said he expects to be acting governor for maybe another three weeks,

"The problem is that obviously the governor needs a lot of physical therapy that's grueling and fatiguing or whatever," said Codey, D-Essex. "It all depends upon him. Does he want to do it when he gets out of the hospital right away, or does he want to wait a little while until he starts his rehab and gets it under way? It's his call."

Spokesman Anthony Coley said Corzine would do his rehabilitation work from the governor's mansion in Princeton once he is released from the hospital.

Meanwhile, workers are getting ready for the governor to resume his duties even before he's able to return to the Capitol. They've been installing fiber optic cable into the governor's office to allow Corzine to do video conferencing, Coley said.

"He's still got a good mind," Codey said. "He devours detail, and so he'll be engaged mentally, that's for sure. He just won't be able to do the physical part in terms of what you have to do outside the doors of the office."

Tom Shea, Corzine's chief of staff, said there's no rush to get Corzine back to work.

Shea said that decision will be made in consultation with Dr. Steven Ross, head of trauma at Cooper University Hospital in Camden, where Corzine has been hospitalized.

"His return to his work is going to depend on his fatigability, and it's going to be a decision made by the governor and his staff as to whether he is able to meet the bonanza of his position," Ross said.

"I would suggest that he's not going back to being governor if he's on sufficient medication to make him groggy," he added.

Ross said the stress of being governor could slow Corzine's recovery.

"It could if you let him go back to soon and it is our goal to make sure that he is ready for that stress at the time he goes back, and that will be our part of the advice," Ross said.

No one has suggested Corzine won't be back to work in six months, but if he isn't, the Constitution allows the Legislature and Supreme Court to remove the governor from office. That procedure has never been implemented in state history, Williams said.