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How DNA tests work and why they are not ideal – based on the story of an American mistakenly accused of murder

In detectives and movies, DNA tests are often presented as the best way to find the perpetrator of a crime. But in reality it is an intricate procedure that malfunctions.

Lukis Anderson, mistakenly accused of murder because of a false DNA test. Photos The Marshall Project
Lukis Anderson, mistakenly accused of murder because of a false DNA test. Photos The Marshall Project

Over the past 20 years, the technology of DNA tests has grown in the status of an effective way to identify a suspect. Thanks to the procedure it is possible to find the culprit for old and hopeless cases, or to identify the attacker for DNA particles under the victim’s fingernails. This happened with the American Lukis Anderson, who suffers from memory problems. After the discovery of his DNA particles under the nails of the murdered businessman, the police charged the homeless man with charges.

The catch was that Anderson never met the deceased and was in a completely different place during the accident. Further investigation revealed the problematic aspects of DNA tests, which, despite the accuracy, lead to false accusations. The history of the American was told by the magazine Wired.

Where there are no prints

On November 29, 2012, a group of intruders entered the mansion of 66-year-old investor Raveesh Kumra (Raveesh Kumra) in a residential area of ​​Silicon Valley in the town of Monte Sereno. The robbers caught the man in the living room, tied him, closed his eyes with a bandage and sealed his mouth with a thick tape. Then the unknown people went up to the second floor and tied the man’s wife. Taking away everything valuable from the house, the intruders disappeared, leaving the owners bound.

The wife of Qumra managed to get to the phone in the kitchen and call the police. When the patrol patrons arrived and the doctors began to inspect the businessman, they realized that he was dead. The coroner fixed asphyxiation due to the scotch that blocked the man’s access to oxygen. About three weeks later, the police arrested the local homeless Lukis Anderson, discovering the particles of his DNA under the nails of the deceased.

Kelly Kulik, lawyer of Lukys Anderson. Photos The Marshall Project
Kelly Kulik, lawyer of Lukys Anderson. Photos The Marshall Project

“I drink a lot. Maybe I really did it, “Anderson told his state attorney Kelley Kulick (Kelley Kulick) while they were studying documents on the results of the DNA examination. “Shut up, Lukis,” the lawyer interrupted him, aware of the gravity of the situation-the accused was facing a death sentence.

In the 1980s, DNA expertise was still at the initial stages of development – for a successful analysis, specialists needed blood, semen, or human saliva. Everything changed in 1997, when Australian forensic scientist Roland van Oorschot published a scientific paper, proving that DNA can be extracted not only from liquid, but also from fingerprints. The discovery caused a large-scale discussion in the scientific sphere and involuntarily eclipsed another statement by van Oorshock that sometimes people’s DNA even turns out to be where they never were.

The rate of DNA spread

After the discovery of the Australian forensic expert, international laboratories were convinced that DNA quickly spreads over long distances. In one experiment, scientists planted volunteers at a table and handed a jug of juice. After 20 minutes from the chairs, glasses, table and hands of the subjects took swabs for genetic analysis. Although the volunteers did not touch each other, 50% of the people were on the palms of the DNA of their interlocutors. In this case, a quarter of the subjects found parts of those who did not touch even a jug of juice.

Then the scientists found in the room unknown genetic data that did not belong to the subjects. The explanation was just one thing: the volunteers brought in someone else’s DNA, having kissed their beloved in the morning, taking a glass of coffee from the barista’s hands, holding the rail in the metro and so on. In the book ” Inside the cells ” lawyer Erin Murphy (Erin Murphy) says that in a day a person can allocate up to 50 million skin particles.

A Pakistani forensic scientist is studying a DNA sample. Reuters photo
A Pakistani forensic scientist is studying a DNA sample. Reuters photo

The rapid development of technology of DNA tests allows scientists to identify a person only by several genetic cells. But since they may well be in a place where their owner has never even been, this increases the risk of such examinations. In the world there are only a few forensic labs capable of studying the so-called secondary DNA transfer.

There are only a few cases of erroneous accusation of a person in a crime due to a genetic test, but since it is difficult to determine the error, the unofficial figure is probably different. “The problem is that we do not follow such things. For every case, when the system of justice manages to find a mistake, there are a dozen unknown cases, “- says the British forensic expert Peter Gill (Peter Gill).

Case Lukis Anderson led 38-year-old Erin Lunsford (Erin Lunsford) with 15 years of experience in the police. On the order of the investigator, a team of forensic experts passed through the mansion of the murdered man in search of DNA particles: mostly specialists searched for fingerprints, traces of shoes or hair of an attacker.

Erin Lunsford. Photos The Marshall Project
Erin Lunsford. Photos The Marshall Project
In 2013, based on 350 cases of homicides with a sexual motive, Canadian researchers found that about a third of criminals try not to leave their DNA. For example, they are looking for another way to deal with the victim, and not just hammer it to death or strangle, at the risk of leaving prints on the body. The tactics of intruders are working: the police close only 50% of such cases, while investigations with less prudent suspects result in arrest in 83% of cases.

“I do not know what you’re talking about, sir,” Anderson said calmly when Lunsford began questioning him about the connection with the robbery. The detective showed the American photos of the victims and asked leading questions, but the suspect simply was silent or answered in monosyllables. The investigator did not insist – thanks to the DNA test he had to have enough evidence to convince the judge in Anderson’s fault and send him for life, or maybe on death row.

The ghost of Heilbronn

While Anderson was under arrest, his lawyer Kelly Kulik collected all possible documents on the state of health of the defendant, which could mitigate the sentence. The idea was not devoid of logic – most of the childhood Anderson spent on the street with other homeless people, and in adolescence, he was diagnosed with diabetes and psychological deviations. Soon he began to drink and accidentally went out on the road in front of a truck. The suspect survived the collision, but began to suffer from memory loss – at times he could forget the events of several days in a row.

With proper study of the list of convictions of the American, it was difficult to believe in his ability to kill a person: drinking alcohol in public places, riding a bicycle in a drunken state and violating the conditions of parole. The only serious crime – hacking with penetration, for which policemen so caught themselves, in fact looked like a story of an amateur.

As they say in the case file, drunk Anderson broke the window and tried to get through it into the house, but he was immediately pushed to the pavement by the owners. When the police arrived, he stood in the same place, where he fell – stunned and with bruises on his face. Although nothing was stolen, the homeless was accused of attempted robbery. At the same time, his DNA was added to the state database on criminal cases, where Lunsford later discovered it.

The road to the mansion of the killed Raveshi Kumra. Photos The Marshall Project
The road to the mansion of the killed Raveshi Kumra. Photos The Marshall Project
The documents found by Anderson’s state attorney showed that he often found himself in a local hospital. The last time he got there on the night of the killing of Qumra (in his blood they found the equivalent of 21 cans of beer) and discharged only in the morning. Alibi men were confirmed by ambulance doctors, who so often took Anderson, who had already learned his date of birth.

In 2008, German detectives concentrated all their efforts on capturing the Hailebronn Ghost – a serial killer and thief, who killed several immigrants, a policeman and robbed a jeweler. In total, law enforcement agencies spent 16,000 hours investigating the investigation, mainly because the criminal did not have a clear pattern of action, and his DNA was recorded in more than 40 places, including Germany, France and Austria.

Eventually, the detectives caught up with the Ghost – they were an elderly Polka, working at a tampon production plant that police used to collect DNA. Somehow the woman left her genetic particles on the objects, which led to the appearance of her DNA in different regions and countries, on the ground of crimes committed, apparently, by different people. In Anderson’s case, the inadvertent transfer of genetic particles to evidence was the result of bringing him to the dock.

The case with the Ghost proved that the transfer of the innocent’s DNA can occur long before the evidence is passed to the laboratory for analysis. A 2016 study showed that gloves, length measuring tape and investigators at the crime scene can carry genetic particles. Even in laboratories, the risk increases – to check working papers, scientists conducted a DNA analysis on them and found out that in 75% of cases, the folders store genetic fragments of unknown people.

When the district attorney Kevin Smith learned of the new turn in the Anderson case, he was not embarrassed and did not notice the mistakes in the work of the investigators. Instead, he proposed a second version of the events: allegedly, Kumra met with the accused a few hours or days before the murder, and at that moment under his nails was Anderson’s DNA. “We are sure that at some point, we just do not know 24, 48 or 72 hours before the events, their paths intersected,” Smith explained.

Future without errors

Researchers have just begun to study the property of transferring and transferring genetic elements, but they can already answer several important questions. Speaking of the Anderson case, every fifth person carries someone’s DNA under their nails. Its successful detection depends on several factors: the amount (the more cells, the higher the probability), the strength of the contact (the handshake leaves only a small number of elements), the nature of the surface (the chemical content affects the amount of DNA) and the elapsed time (the earlier, the higher the probability to fix the genetic cells).

Australian forensic expert Maria Goray (Mariya Goray) is working on a test that can take into account all these factors. This can help defendants prove their innocence in court if their DNA is found at the crime scene. In addition to Anderson, this test would be useful to the British taxi driver David Butler (David Butler). In 2011, the police found his genetic trace under the nails of a woman killed six years earlier. The defendant stated that he had never met a deceased before, and his lawyer noticed that he could carry a real criminal on the day of the murder, passing him some of the DNA.

The theory did not convince the investigators, but the jury agreed with it. After nine months of imprisonment, Butler was released. “DNA has become a magic bullet for the police. They thought, since this is my DNA, then I’m also a killer, “- said the justified.

Anderson’s lawyer believes that the police lined up the case against him on the basis of a DNA test. If the trial of Anderson reached the jury trial, the outcome of the story could be quite different. A 2008 study showed that in 95% of cases the jury found DNA evidence to be accurate, and in 94% of cases it was perceived as a convincing proof of the defendant’s guilt.

Journalist Wired talked with 11 scientists who study the properties of DNA. All of them believe that the forensic experts, and not the judge and the jury, as now, should give an answer to the question “how genetic particles hit the conventional crime scene”. At the same time, the US continues testing the stop-and-spit system, which allows policemen to stop a passer-by and ask him to provide a DNA sample. Similar practice is already taking place in Florida, Connecticut, Pennsylvania and North Carolina, but any person has the right to refuse.

Closing the case

It was Lunsford who corrected his own mistake, having managed to explain how Anderson’s DNA was at the crime scene. After the ambulance doctors took the American to the hospital, they took the call to the Kumra mansion, bringing on the clothing or tools the genetic particles of the suspect.

At the trial, the lawyers of the three other defendants associated with criminal groups also pointed out that the DNA of their clients was accidentally at the crime scene. However, in the absence of an additional alibi, the suspects were found guilty: one received 37 years in prison, two – a life sentence without parole. Anderson was completely acquitted.

“As lawyers, we were often ridiculed in the courtroom when we talked about the accidental transfer of DNA to the crime scene. It was perceived as a hocus-pocus, like a story from a fantastic book. But Lukis showed that this is real, “Kulik described the results of the trial. The trial took Anderson almost half a year, but, as often happens, he did not receive compensation for a false accusation. He continues to struggle with alcohol dependence and applied for assistance from the social service, which can help him find a home.

“In my heart of hearts, I knew that I did not do it,” Anderson said. He believes that he returned to freedom thanks to the blessing of God, and believes that he is not the only innocent who fell into such a situation. “We need to study much more than just DNA. We need to dig deeper. Rethink. Do everything first, until finally you say “this is exactly what you need.” Because it may not be so, “- concludes the American.

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