How does the use of DNA affect the determination of guilt or innocence in a court of law?

Even with the protections provided for the accused, sometimes innocent men and women are convicted while the guilty party walks free. Improvements in science and technology have allowed for a greater degree of accuracy in the outcomes of criminal trials.

Often seen as a state resistant to change, Virginia was a pioneer in accepting DNA testing as reliable evidence in criminal cases and in establishing a DNA lab and databank. DNA, like a fingerprint, is unique to each person. In 1988, DNA experts stated that the evidence implicating Timothy W. Spencer in four rapes cases would match only 1 in 135 million African American males, the significance being that there were that many African American men in the country. Since that date, DNA testing has improved in accuracy, and laboratories are able to test very small samples.

Groups such as the Innocence Project dedicate their time and resources to clearing the names of those who have been falsely convicted. DNA evidence is essential in this endeavor. Since 1989, 289 people have been exonerated by DNA evidence proving their innocence. 17 of them served time on death row. The Urban Institute recently estimated a wrongful conviction rate of between 8 and 15 percent for all sexual assault cases occurring in Virginia between 1973 and 1987.

Timothy W. Spencer, the Southside Strangler, raped and murdered four women (one in Arlington, two in South Richmond, and one in Chesterfield County). DNA evidence was key in Spencer’s conviction. Judge Roscoe Stephenson of the Supreme Court of Virginia wrote the court opinion in Spencer’s appeal. Stephenson’s opinion established Virginia as a leader in using DNA evidence in criminal cases.

Earl Washington was convicted in 1984 of a rape and murder in Culpeper. After serving 17 years on death row, Washington was cleared when DNA testing proved his innocence. He was released from prison.

Thomas Haynesworth was convicted of rape in 1984. DNA testing in 2009 exonerated him in one of three convictions, but there was no DNA evidence from the other two convictions. Released from prison and employed by the state Attorney General’s Office, Haynesworth received full exoneration from all his convictions from a Virginia appeals court in 2011.

Roger Coleman was convicted and executed in 1992 for a rape and murder committed in 1981. He maintained his innocence up to his execution, but DNA testing conducted in 2006 confirmed Coleman’s guilt.

Joseph O’Dell was convicted in 1986 for a 1985 rape and murder and was executed in 1997 despite pleas from family, death-penalty opponents, and the Catholic Church for DNA testing (which was unavailable at the time of his trial). Virginia did not conduct the testing.

That is the law. Is it justice?

In a criminal trial, why must a prosecutor prove guilt but a defense attorney need not prove innocence?
How does the use of DNA affect the determination of guilt or innocence in a court of law?