Thursday, February 21, 2013

The Role of Blood Testing in Solving Crimes

The Role of Blood Testing in Solving

Blood Testing and DNA


By: Evelyn Pearce

Blood testing involves the meticulous process of processing DNA, a genetic substance called deoxyribonucleic acid, which is found in individual human cells. Today, it is an essential and powerful procedure that involves solving crimes, and is a very accurate criminal tool for justice cases. The last decade has experienced profound technological advances in prosecuting criminal cases as well as exonerating innocent victims of crimes. The use of DNA blood testing insures fairness and accuracy when used to identify persons who are suspected of perpetrating crimes of violence, such as assault and battery, rape and homicide. 

The CODIS system, a DNA database, was implemented by the federal government in the late 1980s to store and exchange DNA profiles on the state, federal and local levels. The CODIS system operates by connecting all law enforcement agencies by sharing DNA evidence from various crime scenes. This allows instant profile matches for individual or serial criminal identification. 

As much as 85 percent of the population are known as “secretors.” Secretors have blood DNA in their bodily fluids. Generally, a concise and complete DNA profile will occur in one or less than 100 billion unrelated samples

DNA Sources

Blood testing for DNA involves gathering samples, preserving them, testing by lab analysis and presenting the findings. Human blood and semen represent the two most popular sources for analysis. Other sources include saliva, hair (with intact roots), vaginal fluid, sweat, muscle and skin tissue, nasal discharge and bone. Such liquids and discharges can be gathered from any items they come in contact with, such as drinking straws, glasses, chewing gum, cigarette butts, sweat or moisture on telephone or musical instrument mouthpieces, postage stamps, muscle tissue and partially eaten food. Cellular samples can be taken from garments and shoes as a result of transfer. Samples that have minute or poor quality DNA include fecal and urine samples, which may still yield enough detectable DNA quantities. 

Blood Testing and DNA Sources

Blood testing for DNA involves gathering samples, preserving them, testing by lab analysis and presenting the findings. Human blood and semen represent the two most popular sources for analysis. Other sources include saliva, hair (with intact roots), vaginal fluid, sweat, muscle and skin tissue, nasal discharge and bone. Such liquids and discharges can be gathered from any items they come in contact with, such as drinking straws, glasses, chewing gum, cigarette butts, sweat or moisture on telephone or musical instrument mouthpieces, postage stamps, muscle tissue and partially eaten food. Cellular samples can be taken from garments and shoes as a result of transfer. Samples that have minute or poor quality DNA include fecal and urine samples, which may still yield enough detectable DNA quantities.

Blood testing for DNA identification is used in many instances, predominately crimes, but it has other useful functions that border on solving mysteries. Rape is a common violent crime which can yield trace evidence of the perpetrator's bodily fluid—semen, saliva (bite marks) and sweat. According to a news story in New York, law enforcement connected 22 sexual assaults to a man who had gone on a terror rampage in the city for a long time: source: Using DNA to Solve Crimes; http://www.justice.gov/ag/dnapolicybook_solve_crimes.htm. The case of the Green River serial killer was finally identified after DNA evidence was gathered and analyzed in 2001.

Blood DNA can be gathered from assaults and homicides where the attacker's blood, hair, skin and other fluids have been left behind. Blood can be found on the victim, ground or floor, an object, weapon, in foot and hand prints or anywhere in the vicinity of a crime. 

Blood DNA analysis allows for singling out multiple blood types from a scene, discovering the number of victims and perpetrators, their genders and any blood type disorders belonging to an individual. Specific blood samples can show distance and travel, direction and escape routes of survivors or perpetrators. The amount of blood left behind where no bodies are evident can sometimes determine whether the injury was fatal due to the amount of blood lost. Blood castoff, droplets and smears of a certain DNA type help in determining the extent of an individual's participation during a crime, denoting a play-by-play scenario of the scene. 

In cases of post-mortem analysis when the identification of the victim is not known, as in burning beyond recognition, drowning or advanced or partial decomposition, DNA testing can identify the individual. Family members can be tested and used as a cross-reference check to further pinpoint identity. 

Crimes that are historic and unsolved can be solved by the use of DNA testing in cases where samples of the perpetrator have been kept on file and later matched to newer crimes. Older and smaller traces of DNA can often determine if a victim has suffered prolonged abuse over a period of time.

Advances in DNA Testing

Efforts are being made to increase the speed, reduce the cost and provide more compact DNA testing equipment to crime laboratories. This will reduce the immense backlog of stored samples and hurry the process of solving cases. Important “DNA chip technology” will use nanotechnology to speed up and bring DNA into finer resolution for more accurate analysis, especially in separating tiny or degraded samples of assailant male DNA. Strides are under way to add multiple DNA examination methods, such as Single Nucleotide Polymorphisms, Short Tandem Repeats, mitochondrial and Y-chromosome identification. Gains include technologies that identify microbial DNA from plants and animals that will link DNA found at a crime scene to victims or assailants. Research and development laboratories are seeking better technologies to more efficiently collect and categorize DNA samples which have resulted in mass fatalities and ecological disasters.

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2 comments:

  1. Thanks Joe,
    Once again you are providing amazingly detailed and accurate information. Makes me more proud of our profession to see the levels od expertise serving this nation.
    Scott

    ReplyDelete
  2. DNA Blood Test Waco TX is very important and beneficial way to find out the actual criminal. In so many cases DNA blood testing proves very helpful to determine victim. Thanks for introducing with this great information.

    ReplyDelete