The troubled actress, 24, arrived on Wednesday afternoon and was still at the facility on Thursday, sources confirm to PEOPLE. She was sentenced to 90 days in jail on July 6 for violating her probation in a DUI case.
Lohan's former girlfriend, Samantha Ronson, who recently defended her ex against attacks from Joan Rivers, visited her at the home last night.
Shapiro, 67, a celebrated lawyer best known for successfully defending O.J. Simpson in his murder trial in the mid-'90s, has been involved in rehab facilities since his son Brent died of a drug overdose in 2005. He also created The Brent Shapiro Foundation to help people deal with drug and alcohol problems, and speculation is that he will take over Lohan's case.
"Robert Shapiro is not yet Lindsay's official lawyer," a source tells PEOPLE, adding that Shapiro connected with Lohan after being contacted by one of her acquaintances. While in the facility, Lohan will be meeting with addiction specialists, so, the source adds, "Shapiro can assess Lindsay's situation before he makes an announcement that he's her lawyer."
Her voluntary admission into the sober house was done in the hopes that her jail sentence would get modified.
"She's trying to make an effort," the source says. "The hope is that the judge either reduces the sentence or tosses it out have have Lindsay stay in a facility instead of jail. The hope is that the judge sees Lindsay getting treatment and put her in an inpatient [rehab] program for 90 days instead of jail. Lindsay is not trying to fight or appeal the sentence, but adjust it."
Adds the source: "She had an opportunity to get into a sober house, so she checked herself into his sober living facility, and he's going to see how she behaves."
And while Shapiro evaluates Lohan's behavior, the source says, she really "needs that help. she has mental health issues that stem back from her father, and the abuse that she watched her mom endure."
Reporting by DAVID CAPLAN