The native Scot made a successful second defence after shaking off a slow start in the opening round to outbox Mitchell and inflict upon the Londoner only his second defeat.
‘The Dagenham Destroyer’ edged a tentative opening round but soon succumbed to Burns’ sharp combinations.
A wicked short left floored Mitchell in round four before Burns went in for the kill and scored another knockdown moments later.
And with seconds left on the clock in the fourth round, the referee stepped in to end the fight as Mitchell’s guard disappeared as he slumped against the ropes amidst another Burns onslaught.
The victory takes the champion’s record to 35-2 with his 10th knockout.
Meanwhile, Northern Irishman Carl Frampton also sent his home fans into raptures after outclassing Canada’s Steve Molitor en route to a sixth-round stoppage to retain his Commonwealth and IBF Intercontinental super-bantamweight belts.
Frampton remained largely untouched as he dissected his opponent in Belfast, scoring several knockdowns and opening up a cut on Molitor before the referee finally ended the abuse .
On the undercard, Paul McCloskey defeated Manuel Perez for the vacant WBA Intercontinental light welterweight title on points in his quest to resurrect his career after losing two of last three fights.
Elsewhere, Krzysztof Wlodarczyk retained his WBC cruiserweight title for a second time against Francisco Palacios after securing a unanimous points decision over the Puerto Rican.
Wlodarczyk beat Palacios by split decision in April of 2011 but was faster and more effective this time as he was judged to have won the bout by margins of 116-112, 117-112 and 116-113.
Wlodarczyk has now successfully defended his title four times since May 2010, when he took the title from Italy’s Giacobbe Fragomeri.