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SALT LAKE CITY — There are still many unanswered questions about last week's unusual twist in the search for Susan Powell.
Investigators still won't say what led them to abandoned mines near Ely, Nev. But the highly publicized episode has led to speculation about a CSI-style probe involving forensic geology.
The idea goes back at least to Sherlock Holmes; the fictional detective figured out where a man had been by examining dirt on his shoes.
West Valley police probing the case won't say if they found any tell-tale dirt on the shoes, clothing or vehicles driven by Susan Powell's husband.
If not, they may have missed a good bet, according to Bill Dinklage, associate professor of geology at Utah Valley University. He wrote the course description for an upcoming at class on forensic geology.
Any complicated case is like putting together a puzzle. And a piece of the puzzle might be a specific type of soil.
–Greg Skordas, attorney & metallurgical engineer
"With a combination of evidence, it can be very, very useful," Dinklage said.
When they searched the Nevada mines last week, detectives would only say they had new information from an old search warrant. That has caused some outside observers to wonder if they finally received laboratory evidence linking the mining district to Powell's disappearance.
"Certain soils throughout the states have different properties," said veteran lawyer Greg Skordas. "That's what causes them to have different colors."
Skordas is also a metallurgical engineer with more than a layman's knowledge of mines and geology. He's not involved in the Powell case, but he speculates that detectives may have come up with geologic evidence.
"Any complicated case is like putting together a puzzle," Skordas said. "And a piece of the puzzle might be a specific type of soil."
The theory of forensic geology rests on the likelihood that a suspect will unwittingly pick up geologic evidence from a crime scene and bring it home. If he's burying something with a shovel, there may be bits of dirt clinging to the shovel. There may be dust and mud on his shoes or his pants. His vehicle will often stir up dust and mud as the suspect drives back and forth to the crime scene. Some of it inevitably clings to tires or the undercarriage.
If detectives grab soil samples from a suspect right away, trained forensic geologists can examine the sample for geologic clues such as the color and size of particles, as well as the presence of certain minerals, chemicals and fossils. In some cases, those characteristics can be matched to soil conditions at a specific location.
"I would say it really depends on the case," Dinklage said. "Usually you can't pinpoint an exact location. Sometimes you can get pretty darn close, and very often you can get close enough that it's very helpful."
Geologist Raymond Murray, who wrote the first textbook on forensic geology in 1975, said such evidence sometimes pinpoints a unique place where the soil sample must have originated.
"In some cases it can be quite specific," Murray said. "But that depends upon how unusual the minerals are or the particles are that you've identified."
Robert Hayes has done forensic geology in a number of criminal cases. He said soil samples can lead to the right place, but detectives have to seize the opportunity to collect suspect samples early in an investigation.
"An investigator has to be aware of it, or at least think about it," Hayes said. "And often that may not occur."
West Valley police won't say if they took soil samples from Josh Powell's clothing, vehicles or home. Since December 2009, he is the only one detectives have identified as a "person of interest" in his wife's disappearance.