More than £50,000 ($106,000) was raised by Britons - including an apparent group of police - in support of a Portuguese detective who claimed Madeleine McCann was killed by her parents.
The group, some of whom admit they are internet "trolls", gave cash to a web fund for Goncalo Amaral, 57, the Daily Mail reports.
Judges had ordered Amaral to pay Kate and Gerry McCann £395,000 ($838,000) in libel damages after he wrote a book accusing them of murdering their 3-year-old daughter and then faking her abduction.
But a student from Birmingham launched a GoFundMe page to pay for an appeal by the retired officer, who was sacked as head of the investigation after he launched an outspoken attack on British police.
Last month Portuguese judges decided to overturn the payout but the McCanns will now take the case to the country's supreme court.
One of the biggest payments to the detective's appeal fund was £1000 ($2122) claimed to be from a "very large" group of unnamed Met police officers who said they were "outraged" at the way the officer had been treated.
The post accompanying the donation, which cannot be verified, added: "This strikes at the very basis of the way investigations should be conducted, without fear or favour, malice or ill will. The world can clearly see where the malice and ill will are in this case."
Other donors included Tony Bennett, 67, of Harlow, Essex, who has previously been convicted of breaking court undertakings not to publish allegations linking Madeleine's parents to her disappearance.
Many of those who donated gave regular payments and made abusive or sarcastic comments about the McCanns. One made a reference to a sponsored cycle ride done by Mrs McCann to raise funds to support families with a missing loved one.
Jo Petteford gave £50 ($106) to the Amaral fund and posted: "My pledge for Kate completing her bike ride. I am pleased she has helped fund GA's [Goncalo Amaral's] legal fees by her efforts. Way to go Kate!"
Hard questions that need to be answered
After the donors were accused of being "trolls", some were furious, insisting they were "truth-seekers". Others adopted the term as a badge of honour, with one even using the name "Honourable Troll".
Many of those giving cash accused the Government, lawyers and national newspapers of a cover-up and of lacking the 'decency and courage' to tell the truth.
The fundraising page was started by psychology student Leanne Baulch in April last year. She told the Daily Mail: "I set up the page to help him [Amaral] with his appeal because I felt he had suffered an injustice. His assets had been frozen so he had no way to defend himself.
"I'm not anti-Kate and Gerry McCann. I don't know what happened and I don't claim to know. But I do believe there are hard questions that need to be answered."
She said she was "happy" after the latest ruling in the detective's favour. "The people who donated are very passionate and are pro-truth and justice, not against the McCanns," she added.
Madeleine vanished from her family's holiday apartment in Praia da Luz in the Algarve on May 3, 2007, as her parents dined at a nearby tapas restaurant with friends.
Amaral's book, The Truth Of The Lie, was published three days after the Portuguese authorities formally closed the inquiry in 2008 and cleared the couple of any wrongdoing.
Madeleine's parents said the detective had sparked a "massive tidal wave of lies" against them in his book. In an online post thanking his supporters after he won his appeal, Amaral said he felt 'extremely humble'. He added: "None of this would have been possible without you."
In her book, entitled Madeleine, Mrs McCann said: "Goncalo Amaral has been convicted of falsifying statements... Why is this man being allowed a platform from which to peddle his absurd and offensive ideas?"