Forensic science, also called criminalistics, uses scientific methods to help make decisions about laws, especially criminal and civil laws.

During criminal investigations, forensic science must follow rules about what evidence is allowed and how investigations are done. This field includes many areas, such as studying DNA, fingerprints, bloodstain patterns, guns, bullets, poisons, tiny objects under a microscope, and evidence from fires. Today, forensic scientists also examine cyber incidents, like major security problems that cause big financial losses.

Forensic scientists gather, protect, and study evidence during investigations. Some go to crime scenes to collect evidence, while others work in labs, analyzing items sent to them by others. Some help look at numbers in financial crimes, such as banking issues, and may work as consultants, in schools, or for government jobs.

In addition to lab work, forensic scientists give expert opinions in court cases, working for either the prosecution or the defense. While any area of science could be used in forensic work, certain fields have grown over time to handle most forensic cases.

Etymology

The word "forensic" comes from the Latin word forēnsis, which means "of a forum, a place where people gather." The term's history dates back to Roman times, when trials and other legal meetings happened in the forum. This origin explains the two modern meanings of the word: as a type of legal evidence and as a kind of public speaking or presentation.

Today, the word "forensics" is often used instead of "forensic science." The word "science" comes from the Latin word for "knowledge" and is closely connected to the scientific method, a step-by-step process for learning and discovering things. Together, forensic science means using science to help solve crimes.

History

In the ancient world, there were no consistent ways to investigate crimes, which sometimes allowed criminals to avoid punishment. Investigations and trials often used forced confessions and witness statements. However, ancient records include descriptions of methods that later influenced forensic science.

The first written record of using medicine and the study of insects to solve crimes is found in a book called Washing Away of Wrongs, written in China in 1248 by Song Ci, a justice official during the Song dynasty. This book introduced rules for presenting autopsy reports in court, protecting evidence during examinations, and ensuring fairness in forensic work. Song Ci also described ways to clean wounds on dead bodies, use sunlight and vinegar to reveal hidden injuries, and estimate the time of death based on weather and insect activity. He explained how to examine bodies to determine the cause of death and how to tell the difference between suicide and a fake suicide. His book was the first to provide detailed methods for identifying the cause of death.

In one case described in Washing Away of Wrongs, a murder was solved when an investigator asked suspects to bring their sickles to a single location. The investigator tested blades on an animal’s body to identify the type of weapon used. Flies, drawn to the smell of blood, gathered on one sickle, leading its owner to confess to the crime. The book also explained how to tell if a death was caused by drowning (water in the lungs) or strangulation (broken neck bones) and how to use evidence from corpses to determine if a death was murder, suicide, or an accident.

In many ancient cultures, saliva tests were used to determine guilt or innocence, a practice that later influenced the polygraph test. In ancient India, suspects had to put dried rice in their mouths and then spit it out. In ancient China, rice powder was placed in the mouths of accused individuals. In ancient Middle Eastern cultures, the accused briefly licked hot metal rods. These tests were believed to work because guilty people might have drier mouths due to less saliva, causing rice to stick to their mouths or their tongues to burn more severely.

Education and training

Forensic intelligence is a new area of forensic science made possible by advances in technology like computers, databases, and software that manage data. While it may seem new, it shows that forensic experts are becoming more involved in helping with investigations and policing. This change challenges the old idea that forensic science only helps the criminal justice system by providing information. Instead, it suggests that forensic science should study the clues left behind by crimes. Teaching this new approach requires changing how students think about forensic science.

Recent efforts to include forensic scientists in criminal justice and policing show the need for education and training in forensic intelligence. This article says that there is a gap between how well law enforcement and forensic leaders understand forensic intelligence. This gap can only be fixed through proper education.

The biggest challenge in teaching forensic intelligence is creating programs that help leaders make better decisions when handling information. The article mentions two recent European courses as examples of how this can be done, sharing what was learned and suggesting future steps.

The main idea is that focusing on forensic intelligence can help forensic science become more active, improve efficiency, and increase involvement in decision-making. A new challenge for universities is to shift from studying small clues to solving bigger security problems.

In 16th-century Europe, doctors in the army and universities started recording how people died. Ambroise Paré, a French surgeon, studied how violent deaths affected the body’s organs. Two Italian doctors, Fortunato Fidelis and Paolo Zacchia, helped create modern pathology by studying how diseases changed the body. By the late 18th century, books on forensic medicine and public health were written, such as those by François-Emmanuel Fodéré and Johann Peter Frank.

During the Enlightenment in the 18th century, criminal investigations became more logical and based on evidence. Torture to get confessions was reduced, and beliefs in witchcraft no longer influenced court decisions. In 1784, John Toms was convicted of murder because a piece of paper found in his pocket matched a bullet wad in the victim’s head. In 1816, a farm worker was convicted of murder after footprints and fabric impressions near a pool matched his clothing.

In 1885, an article in Scientific American described using a microscope to tell the difference between two people’s blood in a crime case.

Chromatography is a method used in forensic science to separate mixtures. It helps identify small amounts of substances like drugs or poisons. Many labs use gas chromatography/mass spectrometry (GC/MS) to quickly analyze samples.

In 1773, Carl Wilhelm Scheele, a Swedish chemist, created a method to detect arsenic in corpses. This work was later improved by Valentin Ross, who found how to detect arsenic in the stomach. Toxicology, a part of forensic chemistry, studies drugs, poisons, and harmful substances in biological samples. Forensic toxicologists help determine if poisons or drugs caused a death or injury.

James Marsh was the first to use chemistry in forensics. In 1832, he tested a sample for arsenic in a murder trial. His early test failed because the sample changed, leading to the suspect’s acquittal. He later developed the Marsh test, which could detect very small amounts of arsenic. This test was described in The Edinburgh Philosophical Journal in 1836.

Ballistics is the study of how bullets move. Forensic scientists examine marks on bullets and gun casings to identify the weapon used. In 1835, Henry Goddard at Scotland Yard used bullet patterns to trace a murder weapon back to its mold.

Alphonse Bertillon, a French police officer, created a system to identify criminals using physical measurements. Before this, criminals were only identified by name or photo. His method, called anthropometry, was a more reliable way to track criminals.

Questionable techniques

Some forensic methods that were once thought to be reliable have been found to be less reliable or not reliable at all over time. Some such methods include:

Litigation science

"Litigation science" refers to information or data created specifically for use in a court case, compared to data made during regular research. This difference was explained by the U.S. 9th Circuit Court of Appeals when deciding if expert evidence could be used in court. This type of evidence is called demonstrative evidence, which is made by lawyers or legal assistants to help explain ideas during a trial.

Demographics

In the year 2025, there are about 18,500 forensic science technicians working in the United States.

Media impact

Real-life crime scene investigators and forensic scientists say that popular television shows often do not show what their jobs are really like. These shows may make the work seem easier, faster, more exciting, and more glamorous than it actually is. In reality, the jobs are often routine, repetitive, and not as exciting as shown on TV.

Some people believe that these TV shows have changed how people think about forensic science. This change in thinking is called the "CSI effect." It can lead to wrong ideas about how forensic science works. For example, jurors in court may expect to see a lot of forensic evidence before making a decision, which could unfairly influence their judgment. Some researchers suggest that jurors should be tested to see how much they are affected by TV shows like CSI.

Studies have also shown that newspapers can help people learn more about science and technology in a positive way. Reading about these topics in the news may interest people and encourage them to learn more.

Controversies

Some publications, such as the New York Post, have raised questions about certain areas of forensic science, including fingerprint evidence and the assumptions behind these methods. One article noted that "No one has proved even the basic assumption: That everyone's fingerprint is unique." It also mentioned that "Now such assumptions are being questioned—and with it may come a radical change in how forensic science is used by police departments and prosecutors." A law professor named Jessica Gabel said on NOVA that forensic science "lacks the rigors, the standards, the quality controls and procedures that we find, usually, in science."

The National Institute of Standards and Technology (NIST) has studied the scientific basis of bite-mark analysis, a technique that compares marks on a victim's skin to a suspect's teeth. NIST reviewed the findings of a 2009 study by the National Academies of Sciences, Engineering, and Medicine, which examined the reliability and accuracy of bite-mark analysis. The study concluded that there is not enough scientific evidence to support the use of this technique. However, bite-mark analysis is still legally allowed as evidence in court. In 2019, NIST funded a meeting with dentists, lawyers, researchers, and others to discuss ways to improve this field.

In the United States, on June 25, 2009, the Supreme Court ruled in the case Melendez-Diaz v. Massachusetts that crime laboratory reports cannot be used against criminal defendants in court unless the analysts who created them testify and are questioned by the defense. The Supreme Court referenced a report by the National Academies of Sciences, which stated that forensic evidence is not immune to errors. Justice Antonin Scalia, writing for the majority, cited a report from the National Research Council, which noted that "Forensic evidence is not uniquely immune from the risk of manipulation."

Another issue in forensic science is the lack of laws requiring forensic labs to be accredited. Some states require accreditation, but others do not. This has led to poor work in some labs, resulting in incorrect convictions or acquittals. For example, an audit of the Houston Police Department in 2002 found that the lab had created false evidence, which led to the wrongful conviction of George Rodriguez for the rape of a 14-year-old girl. The former lab director estimated that between 5,000 and 10,000 cases may have been affected by improper work.

The Innocence Project, which tracks cases where DNA evidence cleared wrongfully convicted people, reports that forensic science errors contributed to about 39% to 46% of wrongful convictions. According to the National Academy of Sciences report Strengthening Forensic Sciences in the United States, part of the problem is that many traditional forensic methods have not been scientifically tested. Another issue is that forensic examiners may be influenced by biases and should avoid receiving information that could affect their judgments.

Studies have found differences in how rape-related injuries are reported based on race, with white victims reporting more injuries than Black victims. However, current forensic techniques may not detect all injuries on different skin tones. More research is needed to determine whether these differences are due to skin color affecting how injuries are identified or if darker skin provides some protection. In clinical practice, one study suggests that for patients with darker skin, examiners should carefully check areas such as the thighs, labia majora, posterior fourchette, and fossa navicularis to ensure no injuries are missed during examinations.

Forensic science and humanitarian work

The International Committee of the Red Cross (ICRC) uses forensic science to help find out what happened to people who are missing after wars, natural disasters, or during migration. This work is part of its efforts to help families reconnect with missing relatives. Learning what happened to a missing family member can help families deal with their sadness and move forward in life.

Other groups also use forensic science to find missing people. For example, the Argentine Forensic Anthropology Team works to find out what happened to people who disappeared during the military rule in Argentina from 1976 to 1983. The International Commission on Missing Persons (ICMP) used forensic science to find missing people after conflicts in the Balkans.

Experts recognized the importance of forensic science for humanitarian work and for helping governments investigate human rights violations. In the late-1980s, a group of experts created a UN Manual called the Minnesota Protocol to guide how to prevent and investigate unlawful, sudden, or unfair killings. This document was updated and republished in 2016 by the Office of the High Commissioner for Human Rights.