Matching Unknown DNA to a Suspect

After finding DNA at the scene of a crime, CSI’s must then find out who left the DNA there. Forensic scientists will attempt to match the unknown DNA to a potential perpetrator.

When crime scene technicians find DNA such as semen at the scene of a crime and collect it, they must undergo the task of determining whose it is whether it is the victim’s or the suspect’s. You have seen crime lab technicians on CSI inject fluids into this rectangular medium containing a colorless gel. Then you see these little bands spread out within the gel. Just what exactly are those bands within the gel and how do they tie a criminal to the scene of a crime?

In this article, I will explain what those bands of DNA are and how forensic scientists use these bands to make comparisons of unknown genetic material found at the crime scene to known suspects.

When a forensic scientist comes across unknown bodily fluids containing DNA, they use a gadget called an electrophoretic gel. This gel is divided into several parallel columns called lanes. A DNA sample is then injected at the beginning of each lane just like you see on CSI. The scientist then runs the gel on an electric current which causes DNA fragments in each lane to move creating these bands are spread out through the entire length of each lane. Each sample of DNA separates into a series of bands determined by the size of the various fragments in each sample. The unique bands are then compared, and the unknown bands in one lane are compared to the known bands in another lane. If a lane containing unknown DNA has the same band pattern as that of a lane containing known DNA, this is a positive match. Technicians can make this comparison visually or with the help of a computer.

The samples put at the beginning of each lane are variable. Some are control samples taken from bacterial, viral, or lab-synthesized DNA. These samples contain DNA fragments of known sizes and can be used in determining the sizes of fragments in any unknown samples. Furthermore, one column contains the crime-scene sample, and the other columns contain samples taken from any suspects. For instance, suppose that an offender cut himself at the scene of a homicide, and crime scene technicians found and collected it.

The offender’s blood would be considered the unknown sample of DNA because nobody knows whose it is. When a list of suspects involves three people, DNA samples are taken from each one of them because they are considered known samples. The process of DNA fingerprinting compares the suspects’ DNA with that found at the crime scene.

No two people have the same DNA fingerprint except for identical twins. If this is the case, authorities can still determine which twin is which by their unique fingerprints. Now that you know what electrophoretic gel and DNA bands are, you will have a better understanding of them the next time you watch your favorite CSI TV program.

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… in research because its genes are easier to "knock out" than those of other plants. Previous work has also shown that DNA introduced into Physcomitrella cells is capable of self-replication through an as yet uncharacterised process. …   Read more…

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Forensic Psychology

Want to know more about forensic psychology? Read on to know more about Forensic Psychology and the various functions of a forensic psychologist…

What is Forensic Psychology?

The word ‘forensic’ is derived from the Latin word ‘forum’ which was the place of public gathering in the Roman cities where the process of justice was carried out through debates. Thus, when the legal system is combined with the practice of psychology, we have a study of forensic psychology.

‘Forensic Psychology’ is therefore defined as ‘an intersection between Psychology and the Criminal Justice system’.

Thus, forensic psychology consists of understanding criminal law, make legal evaluations and interact with judges, attorneys and such other legal professionals. It also includes the capability to take psychological findings and translate them into the language of the law, so that the information is understood by the legal practitioners. Towards that end, it is essential that a forensic psychologist understand the philosophy of the law and legal processes.

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The questions that are normally asked to a forensic psychologist are not regarding psychology, but legal questions where the forensic psychologist must be able to convert psychological data into legal language for the court.

A forensic psychologist therefore must have had relevant training in psychology, including clinical or counseling psychology and then gain relevant experience in forensic psychology by working with other practitioners and gaining experience and expertise in one’s field.

Therefore, a forensic psychologist is very different from a typical clinical psychologist. A forensic psychologist does not see the situation from the client’s perspective; neither does he empathize with the client. During the process of a forensic psychological evaluation process, therefore, it is important for the forensic psychologist to examine the consistency of factual data across several sources.

Forensic psychologists thus find employment in different places such as community mental health centers, juvenile detection facilities, jails, prisons, state hospitals, federal and local law enforcement agencies, colleges and universities. Forensic psychologists can also have their own private practice.

Forensic Science Career Options

Functions of a Forensic Psychologist

There are several functions of a forensic psychologist. The primary function is to provide testimony in court. This has grown to become quite a daunting task because attorneys have now become quite competent at undermining the testimony of these psychologists in the court of law.

Apart from this primary function, forensic psychologists also perform various other functions. They are:

Competency Evaluations:

The forensic psychologist is usually appointed by the court of law to assess the competency of the individual to stand trial. If the assessment states that the individual is incompetent to stand trial, it will also state recommendations for the procedures to be followed in order to render the individual competent to stand trial. The forensic psychologist may also prescribe medication for the treatment of the individual. If these medications and treatments do not take the required effect, the forensic psychologist may then advise the court to commit the individual to a psychiatric facility till he can be declared competent to stand trial.

Evaluation of Sanity:

The forensic psychologist is appointed by the court to assess the individual’s state of mind at the time of the offense. This also happens when the lawyer pleads ‘not guilty’ stating the reason of insanity.

Malingering:

Often the individual may also fake symptoms of mental illness during competency evaluations. This will often be revealed by the forensic psychologist by observing the individual in other settings, because it is difficult to consistently maintain false symptoms over a period of time. Such offences can also add more time to the sentence of the individual, when found guilty.

Mitigation of Sentence:

An evaluation by a forensic psychologist is very important when considering the mitigation of the sentence for the individual. Even when the individual’s mental disorder does not meet the criteria for a ‘not guilty’ by reason of insanity plea, other considerations such as the individual’s state of mind at the time of the crime, relevant past history of mental disorder and psychological abuse, medical history, family and social history including physical abuse, mental abuse, domestic violence, and exposure to traumatic events and criminal violence are taken into account. The forensic psychologist considers all these factors before making a recommendation to the court about mitigating the sentence of the individual.

Other Evaluations:

A forensic psychologist is also referred while making other evaluations in the legal processes. One such evaluation is to about assessing whether the individual will commit the same crime again, or whether he is still to be considered to be a danger to society. They are also consulted during probation hearings, parole hearings, and also provide their assessment of the individual’s capacity to be rehabilitated after their release from jail. They also provide information about the credibility of witnesses, help select the jury during the process of a trial and also provide profiles of criminals to law enforcement authorities.

Thus a forensic psychologist performs a very important function in today’s world, especially at the junction of law and psychology.

The Ethical Behavior of a Forensic Psychologist | Helping Psychology

The ethical behavior of a forensic psychologist is often a subject of speculation.

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What does a Forensic Toxicologist Do?

Forensic Toxicologists are vital to both the legal and medical industries. They provide invaluable data on poisons for court cases and their knowledge can have a large part in determining the outcome of a case. In the medical field, forensic toxicologists often work for one of the hundred plus poison control centers in the US, or another government branch such as the Food and Drug Administration, Environmental Protection Agency, Occupational Safety and Health Administration, or Consumer Products Safety Commission.

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In order to become certified as a forensic toxicologist, a candidate must first have a Ph.D. or a doctorate usually in biology or chemistry. Some states have exception clauses for those who have worked six or more years in the field. The American Board of Forensic Toxicology is responsible for bestowing certification which is valid for three years. Forensic toxicologists earn the title "Diplomate" after they are certified. A certified forensic toxicologist will have a much easier time qualifying to be an expert witness for court cases if necessary.

FORENSIC TOXICOLOGY AND DRUG DISCOVERY

If a forensic toxicologist’s services are required for legal matters, he is normally given preserved samples of body fluids, stomach contents, and organ parts to test. He will also be able to access the coroner’s report which will tell him about the signs and symptoms the coroner observed postmortem. Since few substances leave a body unaltered, a forensic toxicologist must have a thorough knowledge of how the body metabolizes drugs. First, the toxicologist will carry out a basic acid-base test to extract the drug from the tissue or fluid. Nearly every drug is either an acid or a base; acid drugs are extracted with a lower pH solution and base drugs are extracted with a higher pH solution.

Next, the extracted drug sample is screened to determine what kind of drug it is and then a confirmation test is done to double check the accuracy of the screen test. An example of a screen test is a chemical spot test. This is where the drug sample is treated with a chemical reagent to produce a color change. The confirmation test is usually a mass spectrometry test which identifies the drug’s unique mass spectra "fingerprint". Drug overdose and alcoholic poisonings are the most common causes for a forensic toxicologist to be involved in a legal case. Typically, the toxicologist is not required to give his opinion of whether the toxic levels in the body were enough to kill a person. However, the exacting scientific testing a forensic toxicologist must perform is extremely important to the outcome of court cases.

Dr. Nachman Brautbar is a board-certified internist and nephrologist, with a specialization in toxicology. He specializes in the toxicological and internal medicine aspects of injury in the workplace, product liability, personal injury, standard of care. To find out more, please visit http://www.environmentaldiseases.com.

Types of Forensic Science | Athens Learning | College Preparedness …

Forensic toxicology refers to the use of toxicology to aid medico-legal investigation of death using poisoning. Several toxic substances do not produce characteristic lesions.

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For more information about Forensic Toxicology, as well as other forensic specialties, check out All-About-Forensic-com, a comprehensive forensics website maintained by two forensic professionals.

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