Tag Archives: forensic science

New Study on Survivability of DNA Evidence

A new study published by the NIJ, demonstrates positive recovery of DNA for up to 10 days following intercourse. Given various circumstances that may lead to delays in reporting or testing, it’s good to know that current testing methods may still yield results even with a substantial delay.

The study can be accessed here (in .pdf format):  https://www.ncjrs.gov/pdffiles1/nij/grants/248682.pdf

Crime Scene Investigation and Fingerprinting

Interesting historic video on crime scene investigation and forensic science. I have a copy as well, that I purchased on DVD from the National Archives. The date on the original is a bit unclear, but it appears to have been made around 1960. It should be noted that some of the practices shown are no longer up to date, and that current safety precautions are not in use. It’s still interesting from a historical standpoint.

Forensic Science Hollywood Style

Just what is the impression of forensic science held by members of the general public (our pool of jurors)? If they believe everything they see on TV or in the movies, they are being sadly misled. Our local attorneys believe that, at the very least they have been generally misinformed about the likelihood of finding fingerprints by exposure to the media. Because of this I will be in court in the coming weeks giving testimony on the difficulties of recovering fingerprints from duct tape… Of course the same attorney moments later mentioned how unusual it is to recover fingerprints from guns- Which he felt had good surfaces for recovering fingerprints. (I re-educated him on this point, as guns have generally lousy surfaces, not to mention all the handling involved in firing/recovering/and making safe prior to processing).

It has been my experience that not only do members of the general public have a lack of understanding of forensic science, but that police officers, detectives, prosecutors and judges are often not much better. I think this trend is likely to continue as long as forensics is misrepresented in the media. People tend to refer to personal experience when assessing the value of new information, and when the personal experience with forensic science is “I was watching Law and Order on TV the other night and they…. ” Continue reading

61st District Court v Heisenberg et. al.

“Wizard’s First Rule: people are stupid…given proper motivation, almost anyone will believe almost anything. Because people are stupid, they will believe a lie because they want to believe it’s true, or because they are afraid it might be true.”
-Terry Goodkind, Wizard’s First Rule,Tor Books, 1994.

“To a jury about to convict a man of a capital crime, any doubt is reasonable.”
-Commentary on the O.J. Simpson trial.

In recent months I have had two different District court judges, lower two different counts of Home Invasion to either Unlawful entry, or Trespassing. Their reasoning? One said that even though we identified the defendant’s fingerprints on an item in the residence which was handled, but not taken. Even though he had no business being in the residence- because there were other fingerprints which we did not identify (we eliminated a number of prints belonging to the owner and his family) we could not show that the defendant had any intent to commit a larceny, one of the “unidentified” persons could have committed the larceny. Continue reading

Trace Evidence: Hair

by Kathy Steck- Flynn

Edmond Locard was the founder of the Institute of Criminalistics at the University of Lyon in France. Locard believed that that when on person came in contact with another person or object a cross transfer of minute particles occurred. This theory became known as the “Locard Exchange Principle”. Locard believed that crimes could be solved by inspecting the “dust particles” carried to and from a scene. This science is known today as criminalistics and has led to the rise of the forensics laboratory (from Mount Royal College background notes FORE 4407 section 3: Unit 4) Francois Goron, head of the French Surete, seems to be one of the first modern investigators who tried to use hair to identify a killer. In his first case hairs found clutched in a dead woman’s hand could not be identified as human simply because there was no information on the subject.

The inability of the scientific community to distinguish between animal and human hair raised interest in the analysis of hair. In the years that followed researchers began to collect information about the structure of human and animal hair (Block, 1979). In 1899, several years after his original failure, in a case known as “L’affaire Gouffe” Francois Goron was able to establish that a murder victim’s hair had been dyed. Establishing this simple fact led to the identification of Gouffe’s body and subsequently to the arrest of his killers (Block 1979). Francios Goron had successfully used forensic hair examination to solve a crime. Continue reading

Interpretation, Collection and Preservation of Glass Fragments

By Kathy Steck-Flynn

A man is found dead in an abandoned house. Upon examination the medical examiner finds that the man was killed by a single gunshot to the head. Three local teens where observed near the house two days earlier. They are picked up and questioned by police. When pressured, the teens admit to having stolen one of the boys’ father’s guns. They had taken turns shooting at the windows of an abandoned house.

The teens admit that John shot the gun first, then Jay and last was Fred. At the scene the investigators find three bullet holes in a window. They analyze the angle of each bullet hole in relation to the victim and find that the bullet which passed through the far right side of the window pane is the one which fatally wounded the man. Continue reading

Ninhydrin Processing

By Pat A. Wertheim

This article originally appeared in Minutiae, the Lightning Powder Co. Newsletter, #45, November-December 1997.

Perhaps the most productive and cost-effective method of developing latent fingerprints on paper is treatment with Ninhydrin. Freshly-mixed Ninhydrin solutions are less expensive and more dependable than premixed aerosol cans or pump spray dispensers. While the premixed containers are ready for instant use when purchased, safety experts today caution against spraying and instead encourage either dipping or painting to apply the solution.

The problem with spraying Ninhydrin solutions is that, even in a fume hood, airborne particles of Ninhydrin dust can form as the carrier evaporates. These microscopic particles may not be effectively removed from the lab by the fume hood, and may find their way back into the air you breathe. Since Ninhydrin reacts with amino acids, any exposure to your body, especially to your eyes or lungs, could have serious results. This potentially dangerous exposure is minimized by dipping or painting. Continue reading

Atmospheric Superglue Method

By Pat A. Wertheim

This article originally appeared in Minutiae, the Lightning Powder Co. Newsletter, #44, Sep-Oct 1997.

Some latent print technicians believe superglue should be listed second only to powder as the most effective latent print development technique. Others believe it should come first. Either way, no one can deny that superglue fuming is the most revolutionary new method to be discovered since the invention of powder. Superglue fuming works on many surfaces where powder is ineffective, such as plastics, and has the advantage of fixing the print on the surface for later presentation in court. Continue reading