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Lindsay Lohan has been ordered to appear in court on Friday, where Beverly Hills Superior Court Judge Elden Fox will consider whether the troubled actress should be sentenced to more jail time as a result of two failed drug tests, just weeks after being dismissed from rehab.

And according to Robin Sax, a former California state prosecutor, not only is there a good chance Lohan will have to spend more time in jail, she may very well have to start serving out her sentence immediately after Friday’s hearing.

RELATED: 'Lindsay Does Drugs Because She's Bored,' Pal Says.

“I just don’t see how the judge could turn around and not give her jail time in this case – and there is a chance he will take her into custody right then and there,” Sax told Pop Tarts, adding that Fox will most likely “up the ante” to sentence the starlet to a minimum of 45 days behind bars, potentially without the early release that she was previously granted due to prison overcrowding.

“Jail didn’t have the deterrent effect they (the authorities) had hoped,” Sax added. “Right now, Lindsay has lost all creditability. It doesn’t matter what comes out of her mouth or how much she says she is going to change – it has come out of her actions because no court is going to believe a word."

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Fox previously warned Lohan that she would have to serve 30 days in prison per violation, however that is entirely his discretion. And although our experts predict it isn’t likely, another scenario could be that the 24-year-old does no further prison time at all.

“The judge can find her in violation, or not, and then the judge will offer a variety of remedies including jail, a program, testing, or nothing at all,” criminal defense attorney Jeffery K. Rubenstein said. “Lindsay could admit the violation and say, ‘Yes, I screwed up’ and ‘I'm willing to go back on daily testing and go back to being an inpatient.'"

Sax confirmed that in Lohan’s situation “nothing is set in stone” – and any further sentencing or court-ordered time spent in rehab is to be determined by Fox.

However, just the day before it was revealed that the “Mean Girls” star had failed mandatory drug tests – her good friend, celebrity photographer Tyler Shields (who shot the recent controversial photos of Lohan surrounded by blood with a gun in her mouth) was confident that she was doing well.

“She is great, she is doing great,” he said. “My experience on a personal level with Lindsay Lohan is that she is a business woman, who at 24 is running more businesses than most people ever will in their whole life and she is under a microscope that maybe .1 percent of people who live in the entire world will ever understand.”

The two apparently even spoke that week, engaging in some creative brainstorming.

“Lindsay is an incredibly intelligent girl. People have their own opinions of her, they have their own opinions of everyone, but she is honestly, amazing. She is a great, great person and I had a conversation with her the other night for two and a half hours,” Shields added. “She was just telling me ideas she had for me, things that I should do, not even with photos, but other business ideas. They were all great business ideas, and she is very savvy, very smart, and I will say I've been with her and experienced what it's like to be chased by 10 cars that are trying to run you off the road and I'm a grown man, and I've raced cars, but watching a 24-year-old girl try to drive through that, it's things like that that people don't have any idea about. Until you experience it, you never know.”

Deidre Behar contributed to this report