NEW YORK — Lil Wayne's gun possession case is putting a leading edge of DNA science under a microscope.
As the Grammy-winning rapper sat in a Manhattan court on Wednesday, a hearing began on a debated, highly sensitive DNA profiling technique used to tie him to a gun found on his tour bus in 2007.
Proponents see the process, sometimes called low copy number DNA profiling, as a powerful tool for closing cases by identifying people from the DNA in just a handful of cells. Skeptics question its reliability.
For Lil Wayne, it could be a crucial piece of a case that carries a minimum 3 1/2-year prison term if he's convicted. He has pleaded not guilty to illegal gun possession charges. The hearing on the scientific status of the DNA technique is expected to extend for days; his trial is due to start Jan. 20.
Prosecutors say small amounts of DNA found on the loaded weapon connect it to the platinum-selling artist. Defense lawyer Stacey Richman says the gun wasn't Lil Wayne's, and the testing technique is too problematic to prove otherwise.
The dreadlocked rapper at times watched attentively through black-rimmed eyeglasses Wednesday as the hearing drilled down on forensic science that operates on a trillionth-of-a-gram scale.
The technique – also known as low-template, high-sensitivity or touch DNA testing – has been credited with helping solve a number of criminal cases, particularly in the United Kingdom.
But it also has come under criticism. U.K. authorities temporarily stopped using it in 2007 after a judge questioned its accuracy and acquitted a suspect in Northern Ireland's deadliest terror attack, a 1998 bombing that killed 29 people in Omagh. Officials ultimately concluded the method was sound and continued using it.
In the U.S., a Queens court has been assessing the technique for more than a year as part of a case against a man accused of killing a woman he had previously been charged with raping.
Methods for testing DNA samples smaller than roughly 16 human cells began emerging in the late 1990s. There are a few strategies; a common one – used in the Lil Wayne case – involves undertaking additional rounds of a molecular copying process used in all DNA analysis to generate enough material to test.
"The only difference is: We make (the test) more sensitive – in other words, turning up the volume," Theresa Caragine, a forensic biologist with the city medical examiners' office, testified Wednesday. The agency triple-checks results to safeguard against anomalies that can crop up during the process.
The technique sometimes can mine IDs from items someone merely touched. Results have been used in criminal courts in at least 10 countries and more than 40 New York City cases, Caragine said.
But some experts say the combination of small samples and more processing is too prone to contamination and murky results to be conclusive – including on the question of how a DNA sample ended up where it was found.
The smaller the sample, the less certain the person actually came into direct contact with the item, rather than touching something else that later touched it, said Dan Krane, a Wright State University molecular biologist and DNA-evidence consultant working on Lil Wayne's defense.
"The weight that can be attributed to the evidence, at the very least, has to go way, way down," he said in an interview.
Police pulled over Lil Wayne's tour bus in Columbus Circle on July 22, 2007, saying they had seen and smelled marijuana smoke wafting out the door before the bus left a concert venue minutes earlier. They said that as an officer approached, the rapper tossed away a Louis Vuitton bag containing the gun.
Richman has disputed officers' basis for searching the bus and noted that more than a dozen other people were aboard.
Lil Wayne, 27, also faces a March trial in Arizona on felony drug possession and weapons charges. He has pleaded not guilty in that case, which arose from a January 2008 arrest at a U.S. Border Patrol checkpoint.
The rapper, born Dwayne Carter, won last year's best rap solo performance Grammy for "A Milli." His albums include "Tha Carter," "Tha Carter II" and "Tha Carter III."