Investigators Hope Public Help Will Strengthen Case Against McCann Suspect

Parents of missing girl Madeleine McCann, Kate (L) and Gerry McCann (R) pose with an artist's impression of how their daughter might look now at the age of nine ahead of a press conference in central London on May 2, 2012 five years after Madeleine's disappearance while on a family holiday in Portugal. Aged three at the time, the artist's impression depicts how Madeleine may now look, based on family photos of her, along with childhood images of her parents. Leon Neal/AFP/GettyImages

BRAUNSCHWEIG, Germany—German and British investigators looking into the disappearance of British toddler Madeleine McCann 13 years ago are relying on hundreds of tips from the public to firm up evidence against Christian B., a suspected rapist they believe murdered her.

The 43-year-old German with a string of prior convictions was living in the Algarve region of Portugal when 3-year-old Madeleine vanished from her bedroom, sparking one of Europe’s largest-ever missing person investigations.