Abstract: A handful of criminal prosecutions have stalled because DNA tests cannot distinguish between suspects who are twins. Then scientists decided to create one. The new experiment called “Eurofin Test” and was done in Eurofins Scientific laboratory. This new method was successful finding an actual suspect among twin brothers.

DNA test has found many uses in the medical and criminal investigation fields. In the medical field, scientists use DNA test to determine paternity. In the criminal investigation field, scientists use DNA test to identify suspects in criminal investigations. However, the DNA test has failed to identify who committed rape between two identical twin brothers which lead scientists to invent a new method in order to distinguish identical twins apart. In the article “One Twin Committed the Crime – but Which One? A New DNA Test Can Finger the Culprit” from The New York Times, on March 1, 2019, it discusses the new method used by the researchers at Eurofins Scientific laboratory to identify the actual rapist among identical twins. This method was successful at identifying the actual rapist, however, the lawyers were against the usage of the new method to prove his/her client as an actual rapist.

The DNA test is a kind of test that could well determine which of the identical twins committed the crime and it could also be practiced for forensic casework as well. Forensic DNA testing arose in the 1990s, years before the first human genome (haploid set of the chromosome in a gamete) was sequenced. “Human genomes are sprinkled with segments, known as short tandem repeats (STRs) and it mutates faster than the rest of the DNA’’ (Zimmer, 2). This rapid changeability to these genetic segment allows scientists to “vary distinctively from person to person’’ (Zimmer, 2). Due to the reason, Researchers have identified 13 specific STRs that were “very effective in matching people to DNA samples” and the probability of the “STRs being identical in two unrelated people is less than 1 in a trillion” (Zimmer, 2). Therefore, DNA testing became a standard legal tool for identifying criminal suspects and resolving paternity disputes.

David Deakin, an assistant district attorney in Boston, used DNA test techniques in two rape cases that took place in 2004. He had been working on a rape case against a man named Dewayne McNair. In 2007, police managed to get DNA from a cigarette Mr. McNair cast away and approached Mr. Deakin to assist them in solving two potentially linked rape cases. Mr. Deakin analyzed samples DNA from Mr. McNair cigarette which showed the STRs were matched to sample from both crime scenes. Therefore, Mr. Deakin came up with a conclusion that they were dealing with one culprit in both cases.

While this may be true, but detectives have discovered that Mr. McNair had a twin brother, Dwight. This makes the case more complex, now, Mr. Deakin got a court order for a new DNA test to investigate furthermore to find out which twin brothers committed rape. The DNA test, unfortunately, failed to determine which of the identical brothers had participated in the rapes. This case was stalled until 2010, when the detective’s tracked down the second rapist in both crimes, Anwar Thomas (Zimmer, 3). Mr. Thomas identifies “Mr. McNair as the other rapist” and states that “he had no trouble telling McNair’s twins apart” (Zimmer, 3). However, these statements wasn’t enough for Mr. Deakin to prove in a jury that “Mr. Thomas was telling the truth” (Zimmer, 3). If DNA test failed to prove who is an actual rapist, it will also not be convincible to identify McNair as an actual rapist just by identifying them apart from each other.

At that time, DNA test was dropping drastically. Meanwhile, a geneticist Dr. Krawczak and his colleagues wondered, “if a test could compare not just STRs but the entire genomes of twins, could it tell them apart”? (Zimmer, 2). In 2012, the researchers suggest experimenting on this method. Afterward, the researchers at Eurofins Scientific laboratory company decided to give the method a try. To begin with the experiment, the researchers have found a pair of twin brothers who “willing to volunteer their DNA, as well as the DNA of one twin’s child and wife’’. They sequenced each person’s whole genome where just a “single mutation, confirmed by multiple analyses”, would be enough to identify which twin brothers DNA match with the child (Zimmer, 3). As a result, the Researchers were successful at identifying the child’s father. After the successful result, it should be conventional to use the Eurofins test in order to find out the actual culprit.

Soon the news reached Mr. Deakin and he became “convinced it could seal both rape cases’’ even though it would be very expensive – $130,000 (Zimmer, 3). Mr. Deakin learned of the Eurofins test and had to drop all the charges against Mr. McNair to make time for the test. After three months, the Eurofins team came up with a conclusion: DNA samples from the rapes match Mr. McNair, not his twin brother Dwight. In 2014, based on Dr. Krawczak statistical analysis, Mr. Deakin told the court that “it was two billion times more likely that the rapist’s DNA belonged to Mr. McNair than to his brother” (Zimmer, 4). This should be an acceptable result because if the test experiment shows the correct result, there is a higher possibility to show correct result in the case as well.

In the other hand, Mr.McNair lawyers filed a motion to exclude the Eurofins test from evidence by claiming that “it was too new and too little studied to be reliable” in order to save Mr. McNair. Judge Linda respect the complicated scientific principles but, in addition, asked to be “replicated by any other lab or to be laid out in sufficient detail in a peer-reviewed journal article” (Zimmer, 4). The decision taken by the judge was also reasonable because if the new experiment done in many other labs and have peer reviews on it, it would be undoubtedly acceptable to others for many cases, especially, for such case like this. Due to the fact, Mr. Deakin had to start the experiment all over again. However, this case was still continued in Boston, with a conventional DNA test narrowing the suspects to the twins and the testimony of Mr. Thomas against Mr. McNair was turned out to be enough to prove Mr. McNair as an actual rapist. As a result, “Mr. McNair was found guilty in January 2018 and sentenced to 16 years in prison” (Zimmer, 4). This shows that the result of the Eurofins test was correct and able to find out an actual culprit related with this case. However, this experiment will continue to help find  an actual suspect in such case like this in future.

In conclusion, the future of the DNA test will balance between law enforcement needs and the public’s right to privacy. Scientists are developing techniques, so, people will be more aware of this and hoping this kind of cases will not happen every day in every laboratory. DNA testing, when used properly, has great benefits to crime investigators and the society in general.

Work Cite

Essays, UK. (November 2018). DNA Testing in the Criminal Justice System. Retrieved from  

Zimmer, C. (2019, March 01). One Twin Committed the Crime – but Which One? A New DNA

Test Can Finger the Culprit. Retrieved from https://www.nytimes.com/2019/03/01/science/twins-dna-crime-paternity.html?login=email&auth=login-email