Boyd's seventh in nine games (74) settled the argument after Lee Ashcroft's 16th-minute goal separated the sides at the break.
Inverness threatened an equaliser in between but it was another fruitless afternoon for John Hughes' visitors, who have won just once in seven games and now sit seven points off third-placed Aberdeen.
Caley Thistle were chasing the game once Ashcroft had headed in Sammy Clingan's free-kick in the game's first significant action.
And they initially made a decent fist of it, Billy McKay looping a header just wide after a decent run from Liam Polworth.
McKay remained his side's likeliest source of an equalising goal, but Craig Sampson kept out his lob shortly after half-time.
And the game was up when Boyd advanced into the area at the other end and beat Dean Brill for his 13th league goal of the season.