Realities of forensic science: Machines can't do it all

By Vicky Wicks, Journal Staff Writer | Sunday, August 28, 2005

Previous Page

Share

• del.icio.us
• Digg
• NewsVine
• Fark

Print

Email

Rex Riis, a criminalist at the State Forensic Laboratory, said there are three primary differences between CSI shows and reality: the time involved in testing evidence, the time it takes to solve a case and what criminalists wear. He added that the state lab doesn't have helicopters and Hum-Vees at its disposal, either.

Of course, programming constraints account for the truncated timelines of television crime solving. Tests are conducted within minutes because television crime fighters have an hour to crack the case. But what gets lost in the translation is the human factor, the need for scientists to visually examine the evidence, make judgments, write reports and undergo a system of checks and balances involving peer and supervisory review.

The Rapid City Police Department and Pennington County Sheriff's Office rely primarily on two labs to do testing for crime solving.

The police department has its own lab in its Evidence Section, with seven employees and two contract chemists, located near the Pennington County Courthouse. The local lab analyzes fingerprints, determines blood alcohol content and tests substances for presence of drugs. Employees respond to major crime scenes throughout the county, according to Lt. Dan Rud.

Also, Police Detective Marcos Glass and Sheriff's Investigator Gordon Decker investigate computer crimes but are not under the umbrella of the Evidence Section, Rud said.

The State Forensic Laboratory in Pierre offers a special agent and nine criminalists who will go to crime scenes at the request of law enforcement agencies throughout the state. And local investigators can send evidence to the state lab for testing and evaluation. State lab criminalists are qualified to analyze fingerprints, DNA, trace evidence, ballistics, electronics (including computer crimes), blood stain patterns, and shoeprint and tire track comparisons.

Autopsies are done by Dr. Don Habbe, a pathologist who works out of Rapid City Regional Hospital.

Fingerprints

Sgt. Mike Jordahl, senior fingerprint examiner at Rapid City's police lab, ran his own fingerprint through AFIX Tracker, the local automated fingerprint identification system, and 17 minutes later had a list of the top 10 possible matches. No picture popped up, and no message flashed on the computer screen. Jordahl's name was first on the list, but he said the first name is not necessarily always the right one.

Because AFIX Tracker is a local database containing prints of people who have been arrested here as well as prints of local officers, searching it takes less time than does a search of the national database.

Chris Reitsma, a state criminalist who specializes in fingerprinting, said a search of AFIS, a three-state database, can take from 20 minutes to five hours. A search of IAFIS (Integrated Automated Fingerprint Identification System), the FBI's national database containing prints of about 49 million adults arrested in the United States, can take anywhere from five hours to three days, depending on how many users are accessing it at the time.

If Jordahl were testing a print for a criminal case, he would look at the top 10 list and determine which ones are possibilities. Then, he would pull files on those and do a visual comparison under magnification of the prints on file with the unknown print. After reaching a conclusion, he would ask forensic examiner Jon Dicks to review his findings. "All disciplines of forensic science have a peer review," Jordahl said.

Both Jordahl and Reitsma emphasized that fingerprint identification relies on a number of variables. First, positive identification is possible only with readable prints, and those are not found at a real-life crime scene as commonly as they are on television. Jordahl said, "When people touch something, they don't necessarily leave prints, or good prints."

If a useable print or partial print is found, identification continues only if the person who left the print at the crime scene has been arrested or is a law officer and has comparison prints on file. And then, a match is possible only if the prints on the ink card were done correctly.

Jordahl said he has never misidentified a fingerprint. When he has finished an examination, he comes to one of four conclusions: the print is identified, the print is not identified, the print has eliminated a suspect or victim or findings are inconclusive, meaning not enough detail was available. When he makes an identification, he said, he is 100 percent sure.

Jordahl and Dicks worked about 400 cases last year, and this year's total will probably be higher. One of those cases required examination of 27 latent prints. About 15 felony cases last year were solved by fingerprint analysis and a search of the local database, Jordahl said.

Jordahl believes in the accuracy of fingerprint identification. Even identical twins, whose DNA is identical, have different fingerprints, he said. DNA is a constant from conception, Jordahl said, but fingerprints form at random and in random sequence before birth. Only permanent scarring, dismemberment or decomposition can alter them, he said.

On television, the processing of fingerprints is not necessarily portrayed accurately. What substance is used to bring out prints depends on the surface the print is left on, Jordahl said.

Fingers leave behind perspiration, which is 98.5 percent water and the rest amino acids and salts, Jordahl said. Also, fingertips leave behind oil that has been picked up from sebaceous gland excretions when touching other parts of the body.

On nonporous surfaces, where moisture remains on the surface, super glue fumes or dusting powders are used to adhere to the moisture, Jordahl said.

To illustrate the effect of super glue testing, Jordahl held up a black pistol mottled with white film that revealed prints.

Fingerprint powder also adheres to moisture, Reitsma said.

Jordahl said if fingerprints are found on a porous surface, such as paper, where moisture has been absorbed, two other substances can be used to bring out prints: ninhydrin, which reacts to amino acids in perspiration and leaves a purple print, or silver nitrate, which reacts to salt.

Fingerprint technology in South Dakota is continually improving. Some jurisdictions, instead of inking prints onto cards, are using live scans, rolling fingers across a computer platen screen that accepts the information and transmits it to the state's system, Reitsma said. The state lab is waiting for its electronics provider to come up with the technology to scan palms, she said.

Jordahl said his lab now has access to IAFIS, a recent development. Previously, the state lab had the only IAFIS access in South Dakota, and because the entire state is allowed only three searches a day, Rapid City had to get permission from the state telecommunications director and the FBI to get one here.

DNA

On television, CSIs find blood, skin, sweat and hairs at a crime scene in the early morning hours and have test results, including name, address and photo of suspect, by noon.

In real life, the state lab is backlogged, and testing DNA takes at least three months, according to criminalist Kandy Smith.

DNA testing became possible at the State Forensic Laboratory in December 2002. Before then, all DNA testing was done at out-of-state labs, and an expert had to travel to South Dakota to testify at trials. The process could be expensive, especially for smaller jurisdictions.

When Kandy Smith receives evidence from a crime scene, she first screens to see if there is anything to test, such as biological fluids or hair. If there is, she extracts DNA from the cell using chemical reagents, enzymes and a buffer solution, she said.

Not all biological samples contain enough DNA for a complete sample. Some samples, such as from hair shafts, will provide only maternal lineage, and others, such as from semen from a male who has had a vasectomy, provide only paternal lineage. These findings give investigators enough information to be helpful to eliminate or interview suspects but not enough to positively identify a person, Kandy Smith said.

Stacey Smith, also a state criminalist working with DNA, said that after unknown DNA profiles are obtained from evidence, they are run through the state DNA database to find a match. The sample is also added to the National DNA Index System, or NDIS, to be searched weekly against other evidence samples as well as convicted offender samples from all over the country. A CODIS (Combined DNA Index System) search is fairly quick compared with fingerprint searches — up to an hour, she said.

CODIS search results do not include a name, much less photo, address or other basic information, Stacey Smith said. Only a DNA profile and a number assigned to the sample come up and can be tracked to a name after a verification process to determine if the samples match, she said.

Trace evidence

When asked for a definition of trace evidence, Riis laughed. "It's that small evidence that's easily overlooked," he said. A more thorough definition would be found in the shelves of books found in the crime lab library.

On television, CSIs put substances into machines and get a printout of the composition; in real life, the same thing happens, Riis said. But the criminalist has to have a good idea what the substance is and will examine the sample under a microscope before testing.

The substance is then tested with gas chromatographs, mass spectrophotometers, or infrared, and results can be ready in minutes. But it takes time and human involvement to prepare the sample, interpret the results or conduct further testing, Riis said.

Electronics

In an episode of "CSI: New York," a surveillance camera records the image of a woman who is sleepwalking. A CSI runs the tape and zooms in on the woman's eye, where the reflection of the real killer can be seen. Possible? Not according to Kendall Light, one of two criminalists at the state lab responsible for examining digital evidence.

Digital photography can do great things, he said, but the CSI:NY scenario expects too much of a surveillance camera.

Light spends much of his time of suspects' computers and searching for evidence in cases such as child pornography, homicide, fraud, identity theft and drug activity.

Finding information on computers is not as reliable in real life as it is on television. Light said that information deleted in Windows stays in the recycle bin until the system needs the space. How long that is depends on how much use the computer gets. The image could still be there a year or two later, or it could be gone in a day.

Deleted information can be found in fragments when Windows overwrites some of the file but not all of it, Light said. All of an e-mail might be deleted from the system at one time, or bits and pieces might be found in different locations on the hard drive.

Forensic pathology

On television, detectives stand by an autopsy table waiting for the forensic pathologist to tell them what happened. That is not how things happen in real life, according to Dr. Don Habbe, a Rapid City pathologist who conducts autopsies at the request of crime investigators. Before examining a body, Habbe wants to hear from detectives. "I'll take all the information the investigator can give me," he said.

"Criminals aren't as smart (in real life) as they are on TV, and the police are good at what they do," Habbe said. Real murders aren't planned, but instead, the murderer is "mad now and grabs what's available," he said. As a result, in most cases, investigators have identified a suspect and know who the victim is before the victim's body is examined.

If the identity of the victim is unknown, identity can be established by the same means as shown on television: DNA, fingerprints and/or dental records, Habbe said. But more commonly, someone knows the victim and makes the identification.

Habbe, one of two forensic pathologists in South Dakota, also conducts autopsies for Wyoming, North Dakota, Montana and Nebraska. He said half of his time is spent doing 180 to 200 autopsies a year and generating reports of his findings, but of those, only 15 to 20 cases are homicides.

The majority of autopsies are completed for public welfare or for the family of the deceased, to determine if survivors should be screened for fatal conditions or treated for infections. Most autopsies, he said, are done "for the benefit of people who are alive."

Contact Vicky Wicks at 394-8318 or vicky.wicks@rapidcityjournal.com