Systematic errors are created through deliberate fraud

From 1993-2008,the same female DNA was found in multiple crime scenes around Europe,incriminating an elusive killer dubbed the Phantom of Heilbronn.But the DNA evidence was so consistent precisely because it was wrong.It turned out that the cotton swabs used to collect the DNA samples had all been accidentally contaminated by a woman working in the swab factory.In other cases, systematic errors arise through deliberate fraud,like the presidential referendum held by Saddam Hussein in 2002,which claimed a turnout of 100% of voters with all 100% supposedly voting in favor of another seven-year term.