Such was the emphatic nature of this ruthless beating, Ross County had the luxury of removing the rampant Boyce with little more than an hour played. He left the field with nine derby goals for the season, 21 in all for the campaign, with County’s sweep of three wins and a draw complete.
Defeat left Richie Foran’s side still five points adrift in bottom place. County move 11 points above them.
Even before half-time, there were chants of “sack the board” from the travelling supporters with Inverness chairman Kenny Cameron also name-checked later.
If County were seeking favourable omens, the game fell five years to the day since they had paraded the First Division trophy through Dingwall by open-top bus, 50 years on since their first Highland League title.
It was predictably fast and furious from the first whistle. County began with a couple of surging attacks, but Caley Thistle quickly retaliated.
Inside four minutes, away striker Alex Fisher showed keen appetite by swiftly shutting down a casual backpass. Goalkeeper Scott Fox had to show deft footwork to clear the danger.
A minute later, from the first corner Iain Vigurs, Inverness captain for the night, picked out the giant Fisher a few yards out but the striker somehow failed to connect.
Jake Mulraney, Caley Thistle’s winger, posed a threat on the left but his searching deliveries drew no end product.
County pressure built towards a 21st-minute opener. Young Jamie McCart’s passback was poorly dealt with by Inverness keeper Ryan Esson whose clearance was blocked by Liam Boyce.
As the loose ball spun across the box, Boyce was sharpest to it and struck his 18th of the campaign with ease.
Caley Thistle woes deepened after 34 minutes. Martin Woods’ corner from the right was knocked away to the far touchline, where County’s Jim O’Brien dispossessed David Raven, and quickly swung the ball to the front of the six-yard box where Boyce was waiting to flick a perfect glancing header over Esson and into the net – his 50th goal for the club.
It was a crushing blow to Caley Thistle spirits and Boyce might have completed his hat-trick three minutes later but stubbed a shot into Esson’s grasp from Gardyne’s fine cross.
Billy Mckay’s entry at the break offered Inverness hope, but for barely four minutes.
Then defender Raven’s clear trip on Martin Woods in the box teed up Boyce for his third from the penalty spot.
Further catastrophe was just around the corner with total collapse facing Foran’s men on the hour mark. Liam Polworth crassly pulled down Ryan Dow in the box, for which the County midfielder was dismissed and Boyce powered in his fourth goal from the penalty spot, his 21st of the season.
All the tension ebbed from the occasion, the outcome now a formality.