HANDS Table of Contents | Chapter 6

Chapter 5

Donita Should Cooperate
with the Police

(or should she?)


The body of a young woman was found in the locker room of the factory where Donita works. Police say the woman was stabbed. The only clues are some strands of hair clutched in the hand of the victim. The hair is not hers, so police think it belongs to the murderer.

According to the factory guards, no outsiders were in the building at the time of the murder. For that reason, police believe the killer is one of the 500 women who work there. But which one? To find out, the police decide to do a mass DNA screening. They ask each worker to give a saliva sample. They want to compare the DNA from the hair to each worker's DNA. If they find a match, chances are they will have the killer.

Donita was friends with the woman who died. For the sake of her friend, Donita feels that she should give police a saliva sample. She figures that it is a painless and simple thing to do. More importantly, she wants the murderer to be found, and she realizes that the DNA screening will flush out the killer only if everyone cooperates. Still, the whole thing makes her uncomfortable. She believes that you are innocent until proven guilty, not the other way around. Donita didn't do the crime, and the police have no reason to suspect she did.

If you were Donita, what would you do?


Everyone has a unique set of fingerprints, which is why fingerprinting is so useful for identifying people. For nearly 100 years, fingerprints have been used to track criminals. They also have been used to identify murder victims and soldiers killed in combat.

Fingerprints aren't always helpful in catching criminals, however. People who commit crimes often remember to wear gloves or at least to wipe away their prints. Even when police find a print, they can only compare it to the ones they have on file. If the culprit has never been arrested before, police won't find a match.

Using fingerprints isn't always useful for identifying bodies, either. Prints can't be taken from a badly damaged corpse such as one burned in a fire, torn apart by a bomb, or decayed. Even when you can get good prints, you need something to match them to. Unless you have an idea of who the person might be, and that person's prints are in records somewhere, the fingerprints from the body aren't of any use.

This is why there is so much excitement about DNA fingerprinting, or DNA typing, as it is also called. In many ways, DNA typing is a much better identification tool than prints from fingers. The actual process involved in DNA typing is quite complicated. What it does, however, is rather simple: It turns each DNA sample into a set of lines, like the bar code you find on the price tags for store products. The lines of one DNA sample can be compared to the lines of another sample to see if they are alike.

A sure match between two samples can be made only if entire DNA sequences are compared. That's such a huge task that it's not yet possible. So what DNA technicians do instead is compare several sections of DNA. If all the tested sections match, technicians can use mathematical formulas to estimate the odds that both samples come from the same person. DNA testing cannot absolutely prove a match, but it can come very close.

One of the great advantages of DNA typing is that there are so many ways to get a "print." You can use hair, blood, saliva, semen, skin, and nail clippings, because they all are made up of cells containing DNA.

For identifying bodies, DNA typing is better than fingerprinting because DNA lasts longer. After someone dies, the flesh decays quickly. This makes it difficult to get fingerprints. However, bones, teeth, and hair last a long time, and DNA typing using these materials can be done long after death.

DNA can also be analyzed for special information that fingerprints don't give. For example, DNA can be used to tell whether two people come from the same family. DNA can also be examined for important clues about persons, such as their gender and other physical characteristics. This might be done if, for example, some bones are found, and you want to figure out whom they belong to.

Uses for DNA Typing

DNA typing was first introduced in the early 1980s. Here are some of the ways it has been used since then:

  • To prove innocence. DNA typing has been submitted as evidence in thousands of cases in the U.S. and other countries. In about one-third of these cases, it has been used to prove people innocent by showing that their DNA does not match the sample found at the crime scene. It also has been used to prove the innocence of people behind bars, including some death row inmates. For these inmates, DNA typing did not exist or was still too new when they were first tried. DNA evidence can last for years, for example, in semen stains on clothing. Lawyers have used this evidence at retrials to show that their client could not be the guilty party because his or her DNA type does not match the evidence.
  • To prove guilt. It is harder to use DNA as evidence to convict a person because juries need to find the defendant guilty "beyond a reasonable doubt." DNA typing by itself leaves some doubt because there is always the chance that someone else besides the accused has matching DNA for the sections that were tested. There also is the chance that someone "planted" the DNA to pin the crime on the accused or that the testing lab has made a mistake. However, testing labs have improved their procedures to reduce the risk of false matches. Lawyers have learned how to combine DNA typing with other evidence to strengthen their case. For these reasons, prosecutors are becoming more successful at using DNA to pin the accused to the scene of a crime.
  • To identify relatives. Children of foreign-born residents of the U.S. and many other countries are allowed by law to enter and live here. Immigration officers have sometimes tried to block the entry of people they suspected were not really the children of legal residents. DNA typing has been used to prove a family relationship and allow legal entry.
  • To prove fatherhood. DNA typing has been used to prove or disprove paternity, that is, whether a man is the father of a child. It has been used in cases where the woman is suing for child support from a man who denies that he is the father. It also has been used in cases where a man wants to share custody of a child but the woman denies that he is the father.
  • To identify bodies. DNA typing has helped identify numerous murder and accident victims. For example, DNA typing was used to identify one of the victims of the 1995 bombing of the federal building in Oklahoma City. Long after all the bodies of the known victims were recovered, a leg was found in the rubble. DNA testing concluded that it belonged to an African-American woman. They used this clue to help identify her.
  • To identify soldiers. The U.S. military used to rely on dog tags to identify the remains of soldiers. Now it uses DNA typing. Blood and saliva samples are taken from new recruits and stored. If that soldier dies in combat and the body is too damaged to identify, DNA from the body can be compared to the DNA in the stored samples. DNA typing was first used to identify soldiers killed in the Persian Gulf War.
  • To uncover history. Examining the DNA of people long dead has been used to reveal information about the past. For example, DNA testing was used to identify the bodies of Czar Nicholas II and his family. This royal family was murdered at the beginning of the Russian Revolution in 1917, and the bodies were never found. In 1995, researchers used DNA typing to confirm that the bodies in a mass grave belonged to members of the Czar's family.
  • To study human evolution. Scientists are collecting DNA samples from people worldwide. They also are collecting DNA from the preserved skeletons of humans who lived thousands of years ago. They are using this information to better understand how the first humans on earth evolved into the many different peoples of the world.

Issues of Privacy

Computers are part of what makes DNA typing such a powerful tool. They can store information from millions of DNA samples. Plus, they can rapidly search through all of this information to find matches. It is this power that concerns Donita, the woman who doesn't know if she should take part in the DNA screening.

If Donita cooperates, her DNA print will go into the police's data bank, along with prints from all the other factory workers. The prints will be compared to the DNA from the hairs found in the victim's hand. Unless those hairs came from Donita's head, her DNA sample should remove her as a suspect.

But her DNA sample may not be removed from the police computer. It may become part of a permanent file. This means that every time the police search their computer to find a match for some DNA evidence found at some crime scene, they will be checking her DNA print. In essence, she will be a permanent suspect.

From Donita's point of view, this is a permanent invasion of privacy. "Privacy" has many definitions. One definition is "the right to be left alone." As long as her print is on file, Donita is not being left alone. She may never be approached by the police again, but they will always be "looking" at her.

Another definition of "privacy" is "the right to decide for yourself what information others can know about you." By giving police her DNA, Donita will be releasing all sorts of information about herself. There is the possibility that they will not only type her DNA, but also test it to learn many things about her. The effect on Donita may be a feeling of loss of control over personal information.

Another concern for Donita is whether the police will keep the DNA information they have on her secret from others. How will the police safeguard these files? Will they permit the use of the files for purposes that don't have to do with law enforcement?

Finally, if privacy is the right to decide what information others can learn about you, it also is the right to decide what information you learn about yourself. If Donita's DNA sample is typed, she may learn some things by accident that she never expected to find out. Perhaps she will learn that she is the carrier of a gene mutation that could lead to disease. Perhaps she will learn that she doesn't share certain genetic traits with her parents and therefore must be adopted. There is all sorts of information that DNA can reveal that people may not want to find out.

Controls on DNA Files

Mass DNA screenings like the one at Donita's factory have been used by police in several regions of the world, including England, Wales, and Germany. A new law in England allows the police to take hair or saliva samples from suspects for DNA typing, even without permission. England also has created the world's first nationwide DNA computer data bank.

Mass DNA screening to solve crimes has not yet happened in the U.S. This country has a strong tradition of protecting privacy. The Fourth Amendment to the Constitution protects citizens against "unreasonable search and seizure." In Donita's case, there is no reason to suspect her of the murder, except that she worked at the factory where it took place. Therefore, taking her DNA might be ruled an "unreasonable search" by a U.S. court. Also, even though she is being asked to volunteer a blood sample, the courts may feel that this is an "unreasonable seizure" because she is being pressured to give a sample.

However, we don't know for certain how U.S. courts would rule. There hasn't been a court case around this issue yet, so we just don't know. It's possible that someday mass DNA screenings could become a common tool of U.S. police.

Even without mass DNA screenings, however, U.S. law enforcement DNA data banks are growing. Many states require convicted felons and sex offenders to give blood or saliva samples for DNA typing as a condition for parole. The idea is for police to be able to use these data banks to catch repeat offenders. The FBI also is building a DNA data bank of criminals. It is possible that DNA samples may someday be taken from people who are convicted of misdemeanors. This means that even if you get stopped for speeding, your DNA could end up in police files.

It is also possible that information from your DNA could end up in other types of data banks. Today, there are many instances where you have to release personal and medical information about yourself. This happens when you apply for a job, for life or health insurance, for credit, for financial aid, or for benefits from the government. If the results of any DNA tests become part of your records, you may have to release the information in order to obtain needed services.

Right now, there are no laws concerning DNA data banks. There is no law which says that a blood sample collected for one kind of DNA testing can't be used for another purpose. There is no law that limits data bank employees from snooping in your files. There is no law that gives you the right to check your DNA file to find out what information is there or to make sure the information is correct.

Some people say that we need to come up with rules for how DNA data banks operate. They say it would be easier to set up the rules now, before the practice of storing and sharing DNA information in computers grows any larger. But technology often moves faster than lawmaking. People may not demand this privacy protection until after they have had their DNA on file somewhere.

Our growing ability to gather DNA information is making many changes in our ways of life. However, it is not just we humans who are affected. The world is also changing for other animals and for plants as well. We look at these changes in our next chapter.


Table of Contents | Chapter 6

Your Genes, Your Choices is a publication of Science + Literacy for Health, a project of the AAAS Directorate for Education and Human Resources. The publication was funded by the U.S. Department of Energy. The website was built by Mike Wooldridge. Send feedback to SciLit@aaas.org.