Born in the UK, Earth in 2175, Portis had an extensive criminal record including several felonies; two murders during a hold-up, one count of manslaughter during a bar fight in Madrid in addition to numerous petty and two grand theft indictments. Towards the end of his six year jail sentence as a juvenile, Nielson's prison psychologist became convinced that he had Psi ability, despite not possessing the mitochondrial marker. Believing him to be one of the 30% of teeps without the marker, Nielson was transferred to a Psi Corps re-education facility but Portis managed to escaped custody while en route.
From 2200 onwards, Nielson's activities had taken on a focus directly related to Resistance activities. In 2204 Nielson was a part of a big Resistance cell in Kazakhstan, UIN along with several other senior resistance fighters including Brazg, Kashiwada, D'Amico, Enoch, Deitz, Klassen and the near legendary Stephen Walters when it was hit by Psi Corps MetaPol forces. While several high profile persons were captured, Walters, Nielson and Brazg managed to escape. Portis eventually linked up with Brazg in Paris, though she had been spotted and followed Psi Corps Cadet Bester since changing trains in Chamonix. Having spotted her tail, the pair captured the young teep and attempted to scan him. During the scan, Bester sent out a deafening mind scream for help, using the temporary distraction to make a break for freedom. Portis got a shot off with his flechette gun and hit Bester in the arm, slowing him down enough so that he and Lara were able to chase him down. However, they caught up to him about the same time as a group of local MetaPol officers. In the ensuing fire fight, Nielson was gunned down while Brazg was arrested and sent to a re-education centre.
- Psi Corps classified Nielson as a "type C blip". A sociopath and a born criminal who had found an organization that validated him and was highly resistant to "re-education."
- After Bester had spent some time with Nielson, he noted that if he had to draw a picture of his mind, it'd be a knife.