Open this photo in gallery The identity of the complainant in the Ottawa case is protected under a publication ban, but The Globe and Mail can identify her as 'L.' Jennifer Roberts/The Globe and Mail

An Ottawa man who raped a 12-year-old girl and then initially got away with it after police dismissed the file as an unfounded allegation has been convicted of sexual interference in the wake of a Globe and Mail investigation.

Brian Lance, 46, was sentenced to five years in prison last week after pleading guilty to the sexual offence.

His arrest came after an Ottawa police surveillance team collected the accused’s DNA off a discarded cigarette. The complainant had become pregnant as a result of the continued abuse and the DNA collected linked him to the child. It was a dramatic conclusion to a case that has spanned two decades and one that the complainant’s lawyer, Blair Crew, said was one of the most remarkable days of his legal career.

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“It’s the first time that I’ve ever seen an offender in an unfounded case being brought to justice. It was astounding,” said Mr. Crew, who has been a leading voice on the unfounded issue and who has counselled at least 100 women who have reported sexual assault.

This case is one of more than 400 unfounded sexual-assault files that have been reopened in response to The Globe’s investigative series. Most recently, on Thursday, the Canadian Armed Forces announced that after a review of 179 military police sexual-assault cases, 23 unfounded complaints required further investigation.

In the past year and a half, at least 100 Canadian police services have audited a combined 37,272 sexual-assault files. It’s unclear how many reopened cases have resulted in charges, but one other complainant featured in the Unfounded series has told The Globe that her case was reopened and charges have been laid against the accused.

Related: Unfounded rates start to fall in cities across Canada

In the recently decided Ottawa case, the complainant’s identity is protected under a publication ban, but The Globe can identify her as “L.” In speaking after Mr. Lance’s plea, L said that while she is grateful he has finally faced legal consequences, it doesn’t change the fact that his actions derailed her life.

Mr. Lance began sexually abusing L when she was 12 years old and he was 26.

In February, 1998, Mr. Lance raped L for the last time when she was 13, resulting in the pregnancy. As she was so young and her menstrual cycles were still irregular, she didn’t realize she was pregnant until she felt the baby kick.

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When L finally told her mother about the pregnancy, she lied and said the father was a classmate at school. She made up the boy’s name. L told police Mr. Lance had warned her that she had better “shut up” about the abuse.

L, whose home life had not always been stable, was forced to give the baby up for adoption. The once vibrant and cheerful student became withdrawn. School records show her grades plummeted. L spiralled. She ended up in a youth jail.

According to an agreed statement of facts prepared by the Crown and defence ahead of Mr. Lance’s plea, the police became involved after L told a worker from the Children’s Aid Society that Mr. Lance was the father of her baby. In March, 1999, the Ottawa Police Service opened an investigation. In a video of L’s interview with police, the teen, then 14, can be seen squirming uncomfortably and occasionally giggling nervously as the middle-aged, male detective pressed her for details of the sexual acts.

When the detective later questioned Mr. Lance, the accused claimed he couldn’t be the father because he was sterile. The officer apparently took Mr. Lance at his word, without collecting any proof. Police made no effort to obtain a DNA sample from the child or Mr. Lance.

The detective also interviewed L’s mother, who relayed the story that L had told her about the boy from school. This called into question the “veracity” of L’s allegation against Mr. Lance, the agreed statement of facts said.

The file was closed as unfounded, meaning the detective believed the allegation to be baseless or false.

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The detective told L’s mother later on that he made the decision based on the fact that Mr. Lance could not father children and that L had giggled while being questioned, which he found to be suspicious. (The Globe has reached out to the now-retired detective on numerous occasions for comment and received no response.)

When The Globe first published details of L’s story in February, 2017, Ottawa police Inspector Jamie Dunlop was quoted as saying that since L’s initial complaint, there is a better understanding around the ways victims deal with trauma. “Laughter is common. Absolutely right. Was that as well known 20 years ago? I don’t know. We’re doing a much better job now of preparing investigators.”

Shortly after The Globe story, Ottawa police reopened L’s case.

Officers focused on the DNA element. L’s now grown child agreed to submit a DNA sample to police. From there, a surveillance team trailed Mr. Lance and collected a discarded cigarette.

On June 21, 2017, Mr. Lance was charged with sexual interference, invitation to sexual touching and sexual exploitation of a young person. On Sept 10, 2018, he pleaded guilty to the first offence in an Ottawa courtroom. The remaining charges were withdrawn. Mr. Lance will be eligible for parole after serving one-third of his five-year prison sentence. He will also be included on a sexual-offender registry for the next 20 years.

Had Mr. Lance proceeded with a trial, he could have faced a longer sentence. In reaching a plea, the accused spared L from having to go through a cross-examination in open court, Mr. Lance’s lawyer, Kate Irwin, told The Globe.

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“It was something he took very seriously from the beginning,” Ms. Irwin said. “Part of what was taken into consideration was the fact that it was a guilty plea and that he expressed his remorse about what happened almost 20 years ago.”

According to those in the courtroom, Justice Trevor Brown told Mr. Lance that had it not been for the persistence of L, he would have been gotten away with his crime.

In a statement to the judge, Mr. Lance said he had lived with the guilt of his actions for two decades and that if he could go back in time and change things, he would.

But for L, the apology was hollow.

In November, 2015, Mr. Crew brought L’s case to Ontario’s Criminal Injuries Compensation Board, which can give financial awards to victims of violent crime. It is not a criminal proceeding and there would have been no consequences for Mr. Lance if he had let L state her case unchallenged. Instead, Mr. Lance showed up to dispute L’s testimony.

“He tried to prevent me from accessing funding for counselling,” L said. “He’s sorry for getting caught. … There was no acknowledgment of the suffering that I’ve been through and the mental-health issues, the suicidal thoughts. I had a complete breakdown."

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The board found L to be “clear, forthright and credible,” while Mr. Lance appeared “vague and inconsistent.”

L, who is now 33, was awarded $28,000.

The following year, she graduated from university.