Trinity had seen a 10-0 lead turned into a two-point advantage for the hosts when Miller tried to reach Sam Williams’ kick between the Saints posts with seven minutes left.
The Wakefield man was barged by St Helens stand-off Danny Richardson as he tried to get the ball down and lost possession.
Referee James Child indicated ‘no try’, but asked video assistant Phil Bentham to check for a possible penalty score.
That was given and Williams’conversion completed a morale-boosting first victory of the season.
Keiron Cunningham, the Saints coach, was unhappy with the crucial decision, but Miller – unsurprisingly – felt Bentham was spot-on.
“I think I score if I don’t get tackled, so I guess you’ve got to award it,” said Miller. “It was a controversial one, but I think he got it right.”
There was an agonising wait before Bentham gave the green light and Miller admitted: “I wasn’t sure. I think the St Helens boys were confident they were going to get the ball back and started walking forward. That put me in two minds, but I thought deep down it was going to be a try.”
Trinity had lost their previous 11 games, a run stretching back to last July and Miller said: “We let ourselves down a bit at the end of last year.
“We haven’t been too far off in the first two rounds, but it is nice to finally get off the mark and hopefully this can be the springboard to a few more wins.
“Full credit to the boys, I think we deserved it. We hadn’t won in a while so getting that first one was very important. We’ve got it now and hopefully it can kickstart us. It was a good one for the boys and there was a lot of happy faces afterwards.”
Trinity have signed utility-forward Dean Hadley on a month’s loan from Hull as cover for Jon Molloy, who has an ankle injury.
Centre Reece Lyne has signed a contract extension keeping him at Wakefield until the end of 2019.