http://www.chron.com/disp/story.mpl/front/3566513.html
STEVE MCVICKER and ROMA KHANNA
"Analysts in two divisions of the Houston crime lab failed to report evidence that might have helped criminal suspects, and they made errors in almost one-third of the cases reviewed in a test sample, an independent investigator reported "
Fourth Report of the Independent Investigator for the Houston Police Department Crime Laboratory and Property Room. - PDF - http://www.hpdlabinvestigation.org/reports/060104report.pdf
For earlier reports see - http://www.hpdlabinvestigation.org/reports.htm