April 4, 2007
Pollen Can Hinder Lifting Fingerprints
ATLANTA -- All the pollen-covered cars in the South may be an eyesore to drivers, but the yellow dust might be a bandit's best friend. Pollen can make it difficult for crime scene investigators to lift fingerprints from outdoor surfaces, since the dust absorbs the moisture people normally leave behind.
In the spring when the pollen is at its worst in the region, police sometimes have to get creative to coax evidence from underneath the sticky covering left by oaks, elms, maples and especially pines - the most popular tree in Georgia.
"We usually try to work our way around it," said detective Rebecca Taft, a crime scene investigator with the Athens-Clarke County Police Department.
In 2005, motor vehicle theft rates in the South occurred at a rate of 7.2 per 1,000 households - a number exceeded only by the West, which had 14.1 per 1,000 households, according to figures from the Bureau of Justice Statistics.
Al Rowland, a crime lab scientist and fingerprint expert at the Georgia Bureau of Investigation, said that even in ideal situations, prints can be hard to lift. Adding pollen to the mix can make it that much harder to track a thief.
"If an item is covered with pollen, the pollen is going to act like dust and the print will never be left on the item that is touched," Rowland said. "About the only way you'd get a print off that is if you touch it, the pollen adheres to the fingerprint ridges and you can see the print in the pollen."
When that happens, a picture might work better than powder. Taft said her department got upgraded cameras last year to take better photographs of fingerprints stuck in pollen. A picture of a good print can sometimes get a hit in the automated fingerprint system.
"That's worked a couple of times," she said.
If that doesn't work, there's a less technologically advanced method: Blow it off.
Around the end of March or early April, wind-pollinated trees like oak, maple, hickory and elm conspire for about a month to make spring miserable across the South. Pine has the biggest pollen grains - which don't wreak as much havoc on allergy sufferers, but they're the ones that coat everything, said Ronald Hendrick, professor of forest ecology at the University of Georgia's Warnell School of Forestry and Natural Resources.
Pollen levels in Atlanta have dropped considerably since last week, when the count was more than 5,000 particles per cubic meter. At times, that number hovered just below the record of 6,013 set in 1999, in the 12 years that the Atlanta Allergy and Asthma Clinic has been keeping track.
The levels are not far behind in the rest of the region. A reading of 120 is considered extremely high in the Southeast. So far, this week's high in Atlanta is 748, set on Monday.
"It seems to be worse than most years," Hendrick said. "On warm, dry days, when it's windy, that promotes the dispersal of pollen. If you part your car under a pine tree, it's going to be covered."
That can be a problem after a break-in, Hendrick said, since pollen provides a fairly rough textured surface that probably wouldn't take prints very well.
Investigator Sybil Warner with the DeKalb County Police Department said she doesn't really consider pollen a problem in her work - unless it rains.
"Rain and pollen is a bad mixture," Warner said. "It's very difficult to try to lift a print through that, because it creates a thicker film."
Dirty cars can also compound the problem, she said.
"With a vehicle sitting outside that hasn't been washed in a long time, the pollen would adhere more to the dirt and dust already on the car," Warner explained. "But a clean car with fresh pollen wouldn't be hard to lift a print from."
Prints buried under pollen can still be lifted if enough of the yellow dust can be cleared, but prints made over pollen might be tougher to get, Warner said. A person's fingertips could remove the pollen without leaving their oil, sweat or other moisture on the surface.
Bobbi Schlatterer, a spokeswoman for the South Carolina Law Enforcement Division, said their investigators don't report any real problems with the pollen. But dry, dusty weather with pollen in the air can affect police work, said Mike Sherman, the crime scene supervisor for the Charleston, S.C., police department.
"We see it every year this time of year when it's real dry out and cars are dusty," he said. "And we see it at construction sites all the time."
Usually police don't like to rely on exterior prints from cars but "in a homicide, you want to get detail from anything, so it definitely can affect you."
"If you're going to get your car stolen, you ought to wash it a lot because that way we'll probably get better prints," he said.
"Smooth and clean is best, and anything other than that gets worse and worse."
Associated Press writer Bruce Smith in Charleston, S.C., contributed to this report.