Nicky Jacobs punched the air after a jury cleared him of the murder of Pc Keith Blakelock.
He subsequently sat down and sobbed before being taken from the dock.
The 45-year-old's supporters in the public gallery including Winston Silcott - whose conviction for the murder of Pc Blakelock was quashed in 1991 - shouted "Yeah, yeah" and called out "Brother, brother" as the verdict was announced.
Courtenay Griffiths QC, for the defence, said: "I'm delighted, I think the jury reached exactly the right verdicts. Now I have to go and see my client."
More top news
Angela Kelly and her daughters, 12-year-old Shanti Harbourne, and Maya-Rose Kelly-Johnson, five, were last seen in Camberley, Surrey.
Voters in part of London have reportedly been turned away from polling booths due to "problems with the lists".
A fire on the tracks this morning at Vauxhall railway station is causing a headache for commuters with disruption until further notice.