Dunfermline were relegated from the Scottish Premier League after Hibernian's first-half goal rush helped consign the bottom club to defeat.
Hibs, needing only a draw to ensure survival and send the Pars down, went ahead with Matt Doherty's header.
Eoin Doyle nodded a quick second and Garry O'Connor's 15th-minute penalty provided further comfort for the hosts.
Hibs were awarded a fourth goal late on but Paul Hanlon's shot did not cross the line after it had struck the bar.
The East End Park side will return to the Scottish First Division after one season in the top flight.
With a five-point gap existing between the sides before kick-off, Dunfermline knew they had to win to take the relegation battle to Saturday's final league fixtures.
But it was Hibs who got off to the perfect start as Tom Soares' deep free-kick was helped on by the head of James McPake and Doherty nipped in to beat Smith with the aid of the post.
Doherty was the provider for the hosts' second, getting the break of the ball on the right and chipping across for Doyle to head home.
And it got worse for Jim Jefferies' side when Austin McCann was penalised for grappling with Hanlon and O'Connor stroked the spot-kick into the net.
Shell-shocked Dunfermline tried to respond and right-back Jordan McMillan joined the attack to force a fine save from Mark Brown.
McMillan then met Paddy Boyle's back-post cross with a powerful header into the arms of Brown.
Pat Fenlon's men weathered the storm and Lewis Stevenson's shot on the break was gathered by Smith near half-time.
O'Connor twisted and turned before firing wide and Doherty was unable to make a good connection on another Soares free-kick early in the second period.
Isaiah Osbourne laid the ball on a plate for Doyle to tap in but the unmarked striker completely missed the ball as it whizzed across the six-yard box.
A free-kick from distance gave Martin Hardie the chance to test Brown and the veteran's shot rebounded off the post, back off the goalkeeper and out for a corner.
Doyle's glancing header was cleared off the line by Gary Mason before Hanlon's well-struck volley from Osbourne's delivery hit the crossbar and bounced down in front of the line but the assistant referee awarded a goal.
And the Scottish Cup finalists made sure of a clean sheet in Fenlon's first home league win when Brown clutched Hardie's dangerous driven ball on the line.