DS MacKinnon was a detective sergeant working in the Weatherfield area.
In November 2016, MacKinnon began investigating Maria Connor after suspicions arose over the disappearance of her flat mate Caz Hammond. Believing that Caz had been murdered and Maria was the culprit, MacKinnon had her arrested. However, it was later revealed by Aidan and Kate Connor that Caz was in fact still alive and was framing Maria in an act of revenge for being evicted from 2a Coronation Street. Despite being released on the charge of murder, Maria was later arrested again due to the fact that she'd revealed to MacKinnon during an interview that she had organised a sham marriage between herself and Pablo Duarte in order to grant him residence in the country. Maria was ordered to serve a twelve month custodial sentence but only ended up serving a couple of months before she was released on a tag.
In March 2017, MacKinnon was the lead officer investigating the brutal attack on Ken Barlow. MacKinnon suspected that someone close to Ken was behind the attack and so called for an interview with all of Ken's closest relatives, Peter Barlow, Tracy Barlow, Adam Barlow and Daniel Osbourne. However, while investigating the family, MacKinnon was led to believe that the attacker was Pat Phelan due to countless reports of him and Ken arguing over the building work going on at 1 Coronation Street. MacKinnon then had Phelan released after Todd Grimshaw was able to provide solid evidence of his whereabouts at the time of Ken's attack (due to him having installed a security camera at 19a Victoria Street).