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History, Evolution and Case Studies of DNA Evidence

If you are accused or arrested for a serious crime in the State of Florida it’s not your responsibility to interact with police if they question you before or after you’ve been read your Miranda Rights.

You have a Constitutional right to obtain legal counsel before you answer questions asked by any type of law enforcement.

It is also imperative to understand that police may lie to get you to make a statement which may or may not incriminate you in a court of law. A law enforcement official who tells you that your DNA was found at the scene of a crime may likely loosen your lips for providing them with vital comments that may later be used against you.

Call Michael B. Cohen, Esq. 24/7 at any of the phone numbers listed above or throughout this Website if you find yourself facing this situation.

Many of us that watch TV drama crime shows come away with the impression that DNA evidence is infallible once found by police at crime scenes which is then positively matched to a suspect in custody or one being sought through investigation for a crime.

Although in many cases the matching of a DNA fingerprint to a suspect can be damning there are cases where its presence and determination of guilt can be undermined by a knowledgeable attorney at trial.

Some instances where this physical evidence can be disqualified include consistency errors made by technicians when building a DNA profile in the lab, including systemic failures that include inadequate supervision, *contamination at the point of collection, inadvertent transfer of DNA evidence to a crime scene by a third party as well as software glitches and misreading results when DNA evidence is tested through computer software, among many other negating possibilities tied to human error that a defense attorney will try to point out to a jury for their client’s benefit allowing for the possibility of demonstrating reasonable doubt.

*The most famous instance of point of collection contamination was during the O.J. Simpson trial when his dream team of attorneys apparently invalidated evidence linking Simpson to the crimes as far as the jury was concerned.

History Evolution and Case Study of DNA used in Criminal Cases

DNA evidence has been legally used by law enforcement, prosecutors and the courts as a tool for deciding innocence or guilt since 1986.

In a case that took place in Leicester, England involving the rapes and murders of two teenagers, which took place in 1983 and 1986 respectively, a man named Richard Buckland had initially confessed to one of the two crimes. Because aspects of the other crime were very similar, law enforcement believed he was the perpetrator of both.

Although no physical evidence implicating Buckland was found at either crime scene his confession was damning for his defense. But although it originally appeared Buckland was the offender, the investigation by police continued.

The Leicestershire Police collected blood samples from approximately 5,000 other local men to be tested for a DNA match. One of the men from the group had previously convinced a friend to act as a replacement when providing a blood sample using his identity. The ruse was discovered when the friend was overheard boasting of the deception as the stand-in for his friend at a local pub.

Colin Pitchfork, the man behind the deception was subsequently questioned by police and his actual blood was then taken for DNA identification. The results confirmed his presence at both murder scenes. Aware of the implications of the DNA fingerprint which had been broadly reported in the press, Pitchfork acquiesced to committing both murders leading to Buckland’s acquittal.

The genetic makeup of all human beings is 99.9 percent identical. The remaining 0.1 percent’s differences hold important clues to each human’s dissimilarities.

Finding a pair of people with the same DNA pattern in four places or more on a chromosome within the remaining 0.1 percent is just about unheard of, except in cases of identical twins. This is the minimum number of DNA areas that labs normally analyze when attempting to find a match in a criminal case. If the results show a total of six DNA segments, that person's pattern is as unique as a fingerprint.

Research completed in Australia recently found that cases of sexual-assault concerning DNA evidence was twice as likely to reach trial and thirty-three times as likely to result in a guilty verdict. In cases of homicides involving DNA evidence they were 14 times as likely to go to trial and 23 times as likely to end with a guilty verdict.

In the United States the first case that utilized a DNA fingerprint to go to trial was the case of a suspected rapist.

In mid-1986, Tommie Lee Andrews was accused of the rape of at least twenty-four women. One of the women; Nancy Hodge was robbed and raped at knifepoint by the suspect of whom she only caught a quick glance which was not enough to physically identify her attacker.

However, during the ensuing investigation, law enforcement was able to retrieve partial fingerprint smudges left behind on a window sill. When questioned by police and giving blood after a warrant was served it was found that Andrews’ DNA fingerprint matched the semen sample retrieved obtained from Ms. Hodge through forensic testing.

Based on this evidence, Tommie Lee Andrews became the first offender to be criminally convicted in a United States court of law by way of DNA fingerprinting evidence in 1987.

He was originally sentenced to over 100 years in prison for rape, aggravated battery and burglary, but the sentence was recalculated to 62 years and was further reduced by about 21 years, due to a law at the time that routinely took off one-third of every prisoner's sentence, according to the State Attorney's Office.

After completing his sentence in 2012 a jury concluded he was a violent sexual predator and sent him to a sexual treatment center under what’s known as a civil commitment act. Due to this assessment, Mr. Andrews will most likely be housed in confinement for the rest of his life. Under the *Jimmy Ryce Act, violent sexual predators can be held beyond their sentences until they can convince a court they’re no longer a danger.

*The Jimmy Ryce Involuntary Civil Commitment for Sexually Violent Predators' Treatment and Care Act was passed unanimously by the Florida legislature and signed by the Governor in mid-1998, becoming effective on January 1st of the following year.

In addition to matching DNA evidence found at crime scenes, law enforcement is now using genealogy services such as and other sites that similar to it to crosscheck and track down potential suspects.

To read a current article that appears on my blog that relates to this topic click here.