Paramedics took the mum-of-two from her Los Angeles home after she locked herself in her bathroom with one of her then toddler sons.
The infamous meltdown occurred on January 4, 2008 – with Britney shaving her hair in a downtown salon just days later.
Her manager at the time Sam Lutfi, who is now suing Spears’s mother Lynne for her description of him in her new book, claims the singer’s amphetamine use was behind her shocking meltdown.
He also claimed that the Grammy winner felt she needed to shave off her hair to hid evidence of drug-taking as she battled ex Kevin Federline for custody of her young sons Sean Preston and Jayden James.
Lutfi’s claims were laid bare in his defamation case against Lynne Spears which is now before a jury in an LA court.
During proceedings yesterday Lutfi’s lawyer, Joseph Schleimer, told the jury Spears had a script for amphetamines filled.
On the day in question, Lutfi claims she took eight pills earlier and several more later that evening before going off the rails.
Mr Schleimer claimed his client tried to get Britney to meet with a psychiatrist two days beforehand – but she refused.
Furthermore, Lutfi claimed that Britney was paranoid her hair contained traces of the drugs she was using at the time.
Mr Schleimer suggested Britney was concerned a judge would test her hair for drug use – and she could lose custody of her two young children if the test came back positive.
In desperation, Britney then shaved off her hair which was famously caught on camera as she believed this was the only way to beat the drug test.
Lutfi is claiming that Britney’s meltdown stemmed from her drug use – and he claimed that she was using crystal meth.
The jury was told that Sam Lutfi used an amphetamine himself – Adderall – which he claimed was for ADD. However, he denies he ever gave Britney this drug.
The jury heard Lutfi’s claims that he repeatedly told Britney she needed to get off drugs – and was talking about bringing in a new team – which he called the Varsity Team – to help save her.
In a bid to get Britney off drugs, Mr Schleimer claimed Lutfi brought in drug-sniffing drugs into her LA home and they found traces of drugs in the carpets. He claimed this was crystal meth.
Furthermore, Lutfi’s team also divulged details of her disastrous VMA apperance in 2007 which saw her mime and dance badly.
Lutfi felt Britney was a mess and shouldn’t do the performance as she was overweight and didn’t rehearse – however, he claims she refused to listen to him.
And Lutfi also claimed that Britney’s father Jamies punched and attacked him while he was working with Britney.
The jury was told that Britney sought Lutfi to manage her, promising him 15pc of her total earnings – this amounted to $800,000 a month, and millions more when she was on tour.
He also claims credit for Britney meeting her current fiance Jason Trawick – he claims he introduced them at Jason’s Halloween party in 2007.
Britney’s side has yet to respond in court – Britney herself will not be giving evidence as a court ruled she is not legally competent to do so.
The trial comes as Britney’s comeback continues unabated with her well-received role as a judge on the US X Factor.
Jurors likely won’t hear directly from the singer. Attorneys for Spears’s parents and conservators will have their own opportunity to present opening remarks to jurors later today, when the trial resumes.
Lutfi is seeking millions of dollars from Spears and her family, claiming her mother’s book lied about him drugging and isolating the pop superstar.
The case is the culmination of years of acrimony between Lutfi and Spears’s family and conservators, who successfully obtained a restraining order against him to keep him from contacting the singer or trying to intervene in her life.
The order has since expired, but conservatorship attorneys are seeking repayment for more than $93,000 (¤71,100) in legal fees – a judgment Lutfi is appealing.
Lutfi sued in February 2009, roughly a year after Spears was hospitalised and placed under the conservatorship to take control of her health and finances.