The miscarriage of justice in the Barker case was due to the mistaken views held by some of the forensic scientists involved in the case, who believed that they owed allegiance only to the prosecuting lawyers  Justice was thwarted because these forensic scientists failed to provide evidence impartially to both the defense and the prosecution
Hence it is not forensic evidence in general that should be condemned for this injustice
Most forensic scientists acknowledge a professional obligation to provide evidence impartially to both the defense and the prosecution.