Two British men found guilty of murdering black teen in brutal attack Lawrence family via PA / AP, fil Gary Dobson and David Norris were found guilty of the murder of Stephen Lawrence, above, at the Old Bailey in London on Tuesday. By NBC News, msnbc.com staff and news services LONDON - A jury found two men guilty on Tuesday of murdering a black teenager in a brutal assault that shook Britain to its roots nearly 20 years ago. Gary Dobson, 36, and David Norris, 35, had denied killing Stephen Lawrence, who was attacked by a gang of five youths and stabbed to death in southeast London in 1993. Prosecutors had claimed that blood, hair and fibers traced to Lawrence were found on Dobson and Norris' clothes, proving their involvement. The defense had claimed the evidence was contaminated. The jury deliberated for three days at the Old Bailey courthouse before announcing the verdict Tuesday. The initial charges against three of the five youths in 1993 were dismissed following a mishandling of evidence by police. Change in criminal law The case has marked a seminal moment in race relations in the UK and has helped modify recent British criminal law. Crown Prosecution Service / Reuters Gary Dobson (left) and David Norris (right) had denied killing Stephen Lawrence in 1993. Two internal police inquiries acknowledged police were not vigorous in pursuing evidence. And a public inquiry, the McPherson Report (1999), led to recommendations in recognizing race-based hate crimes. The McPherson Report also went a step further in acknowledging that racism was an institutional feature of London's Metropolitan Police and recommended that race relations legislation should not only apply to the public but also to the police force. Additionally, Britain's double jeopardy law has been revised to allow a suspect to be tried for a second time over the same crime if new evidence comes to light. With the advances of DNA technology, prosecutors were able to call for a review of evidence against Dobson and Norris this year. NBC News producers Karl Bostic and Jason Jouavel and The Associated Press contributed to this report.