The 37-year-old man, Daniel Nyqvist, who has now confessed to the murders, was 21 years old in 2004 when the murders of the eight-year-old boy Mohamad Ammouri and the language teacher Anna-Lena Svensson occurred one early October morning in central Linköping.
The police got hold of the man by running DNA from the crime scene against commercial genealogy databases.
You then met a distant relative.
With the help of a genealogist, one could then trace oneself to Daniel Nyqvist.
The same method was used in the high-profile American case "Golden state killer".
In June, Daniel Nyqvist was arrested in calm forms by the regional task force in his home in Linköping - and then topped.
The result was a 100 percent match with the perpetrator's DNA from the crime scene.
On the same day, the man confessed to the murders.
Probably answer to motive
The investigation into the double murder has over the years grown and become Sweden's second most comprehensive police investigation ever, only the Palme investigation is more extensive.
But now the investigation is complete and on Wednesday charges will be brought against the 37-year-old.
The act 16 years ago has strongly influenced Linköping and today comes the answer to the question that has plagued the people of Linköping all these years - "What was the man's motive for the act?"
Ships directly
In connection with the prosecution, the Public Prosecutor's Office and the Police Authority have called a press conference on Wednesday, starting at 11.15.
SVT Nyheter reports directly from the press conference in which Britt-Louise Viklund, chamber prosecutor, Jan Staaf, commissioner and Henry Jansén, investigator of the serious crime, participate.