A Scotland Yard officer could face manslaughter charges after an inquest jury ruled Ian Tomlinson was unlawfully killed at the G20 protests.
Jurors delivered a damning assessment of Pc Simon Harwood's actions, saying he "deliberately and intentionally" shoved the newspaper seller to the ground.
The Director of Public Prosecutions will launch a quick and "thorough" review of his decision not to prosecute the officer as the unanimous verdict was returned.
Pc Harwood, a father of two, will also become the first officer to face a public Metropolitan Police disciplinary inquiry.
As family members welcomed "justice" for Mr Tomlinson after a two-year wait, Deputy Assistant Commissioner Rose Fitzpatrick expressed her "profound condolences". The police chief added: "It is a matter of deep regret that the actions of an MPS officer have been found to have caused the death of a member of the public."
Mr Tomlinson collapsed after suffering an internal bleed as a result of the officer's "excessive and unreasonable" force, the jury said.
They discredited evidence from both Pc Harwood and pathologist Dr Freddy Patel.
In a written statement, the jurors told the inquest: "Both the baton strike and the push were excessive and unreasonable. As a result, Mr Tomlinson suffered internal bleeding which led to his collapse within a few minutes and his subsequent death."
Paul King, Mr Tomlinson's step-son, thanked the jury as he spoke of his hopes that the Crown Prosecution Service would reverse its decision last year not to pursue manslaughter charges.
Standing alongside Mr Tomlinson's widow Julia, he said: "After two years, we're really grateful that the inquest process has made a strong statement about how Ian died. We are grateful to the jury and the coroner and we think the jury finding speaks for itself in the verdict of unlawful killing."