Britney Spears and Kevin Federline
INF; Martin Fried/UPI Photo/Landov
01/22/2008 AT 01:05 PM EST
's deposition at the hands of Kevin Federline
lawyer Mark Vincent Kaplan has been an emotionally difficult experience that has only just begun, Kaplan tells PEOPLE.
"We are going over things that are very, very gut-wrenching," Kaplan said Monday night, speaking outside of Katsuya restaurant in Brentwood. He declined to discuss specifics of the questioning
, but said, "Just to revisit them even in your own mind would not be pleasurable."
"It's not something anyone would enjoy," he says.
Spear has a spotty record with past deposition dates in the custody case, missing numerous appointments and sitting for only 14 minutes on Jan. 3. Kaplan is expected to be grilling Spears, 26, about past drug and alcohol use, her failure to comply with court orders and any other subject relating to her fitness as a parent.
After a meltdown and brief forced hospitalization, Spears lost visitation rights
with sons Preston, 2, and Jayden, 1. Ex-husband Federline, 29, has sole legal and physical custody.
Even Monday's session was in doubt.
"She was about 50 minutes late," he says. "After an hour I would have been over it. I was prepared to terminate had she not showed at that time."
Spears was spotted biting her fingernails when arriving to Kaplan's Century City Plaza office. After spending more than two hours there, Spears appeared tense and lit up a cigarette behind the wheel of her Mercedes before driving through Beverly Hills listening to Madonna on the stereo.
The deposition on a national holiday Monday was booked after the shortened deposition on Jan. 3. The holiday booking was done to accommodate busy lawyer schedules, says Kaplan, and it "did dovetail into allowing this to be a low-profile appearance."
Kaplan says there will further depositions in the unspecified future, claiming that he has only worked through "2 percent" of his questions.
"There is a lot of work to be done," he says. But he adds he was heartened by the idea of even having the meeting in the first place.
"She came for her deposition, that's great," says Kaplan. "Showing up is form over substance."
Additional reporting by PERNILLA CEDENHEIM