Mullen was a close family friend implicitly trusted by Chris's family, and he even accompanied the priest on trips to Germany and the United States in the early 1990s, where alleged sexual abuse took place.
More than two decades later the psychological wounds are still raw, with Chris undergoing counselling since receiving news this week that the Vatican had found the cleric guilty and dismissed him from the Church.
However, Chris, who is in his early 30s, says he has sympathy for Mullen.
He said: "I really don't know why, but I do. People have been saying to me I should be celebrating, but celebrating just hasn't occurred to me.
"I've seen some pretty dark times and right now my emotions are totally confused. My parents have finally seen some justice but this has destroyed them. It's been a terrible toll. They trusted this man. My mum no longer goes to church and my faith is another thing I've lost as a result of this too.
"Already this week I've been speaking to counselling teams. You can't go through stuff like that and then talk about it without the dark clouds coming back. This has had me hospitalised in the past.
"I've already lost a job, my home and a long-term relationship over this. I had the lot. Great job, two cars, the dog, loving relationship. But only this year am I getting myself on track with a job and am in a new relationship."
The long-term psychological damage caused by the abuse Chris alleges and the impact it has had on his pursuit of a normal life has seen him go after the Church for compensation, believed to be in the six-figure range.
As well as his own allegations, the priest also faced claims from another man, who was totally unknown to Chris, dating from the mid-1970s.
In January 2012 the Crown decided not to prosecute Mullen, but the Dunfermline procurator-fiscal had previously said the case would remain open for review if other complainers came forward or new evidence surfaced.
Mullen, who was a priest in the same parish as Cardinal Keith O'Brien in the 1970s and later had his friend as his boss when O'Brien became Archbishop, will still get a roof over his head from the church.
It is, after all, an organisation that breaches forgiveness and compassion.
However, for now Chris hopes and believes the move to remove Mullen is indicative of a new broom within the Catholic Church around abuse cases.
Chris added: "In the past this would've been brushed under the carpet. There are good people in the Church who were getting frustrated by the red tape. My parents have finally got the justice they've been looking for. There's a chance there could still be a prosecution, but hopefully others who've suffered like I have will see these things don't always get locked in a cupboard."
His solicitor Cameron Fyfe said: "This is a big step forward. The Catholic Church has said that this abuse happened.
"Abuse like this has an impact on all sorts of areas of life and psychological health. For my client this has also had a very significant impact on his ability to hold down a professional life."