Does every crime leave a trace?
Locard's theory, developed by Edmond Locard, answers this question affirmatively: whatever the steps, the objects touched by an individual, their footprints or fingerprints, their hair, the fibers of their trousers, the blood, or other bodily fluids they leave behind. All of this carries a silent witness, a fragment of evidence to be mapped.
Technology has certainly contributed to solving thousands of crimes that have left a hidden trace, concealed by the various tricks of the criminal. Therefore, considering the possibility of comparing biological material possibly left at a crime scene with the DNA of suspects is yet another innovative perspective from bioethics in the resolution of investigations.
This stems from the high precision of the genetic material contained in DNA. With advances in genetic engineering, it has been discovered that analyzing a person's DNA strands allows them to be distinguished from others, given that each human being has a unique genetic code, except in the case of twins.
In the forensic field, this resource holds valuable weight compared to other evidentiary methods, especially because it achieves results that prove innocence or identify culprits in a more assertive manner.
Genetic profile databases in Brazil
In Brazil, Law No. 12.654/12, which amended Laws No. 12.037/09 and 7.210/84, allowed the collection and storage of data in genetic profile databases for criminal identification purposes, establishing a new form of investigation and contributing to the resolution of crimes, especially homicides and crimes against sexual freedom and dignity.
Criminal identification through DNA is simply another type of identification, just like photographic and/or fingerprint identification carried out in police stations, and supported by article 5, item LVIII of the Brazilian Federal Constitution of 88.
The acquisition of this resource is regulated by Law 12.654/12, and its storage is governed by Decree 7.950/13, which creates and holds the National Bank of Genetic Profiles (BNPG) responsible for managing these materials and investigating crimes, for the benefit of criminal justice.
Beyond its criminal implications, the use of genetic profile databases shows promise in identifying missing persons, where the comparison of DNA samples provided by relatives of victims is carried out freely and voluntarily, which has proven useful even in situations of natural disasters.
Genetic identification and its implications for the Penal Execution Law
According to Article 9-A of the Penal Execution Law, as amended by Law No. 13.964/2019, those convicted of intentional crimes committed with serious violence against a person, as well as crimes against life, against sexual freedom, or sexual crimes against vulnerable individuals , will be compulsorily subjected to genetic profiling through DNA extraction, carried out upon their entry into the penal establishment, after a final conviction with res judicata.
Finally, it should be noted that the convict's refusal to provide biological material constitutes a serious offense, highlighting the mandatory nature of the measure under current legislation.
It is worth highlighting that the reform of the LEP (Law of Criminal Execution), promoted by the 2019 legislation, introduced several provisions aimed at protecting fundamental guarantees, such as the dignity of the human person and the right to privacy and intimacy in the context of genetic identification.
Among these measures, the following stand out: the prohibition of genetic phenotyping and the use of biological material in family searches for criminal purposes (cross-referencing); the requirement to discard samples after analysis; and the guarantee that access to data is carried out in a strict, confidential, and absolutely controlled manner.
Furthermore, the legislator clarified that this is not a DNA bank in the broad sense, but a bank of genetic profiles, composed of fragments that do not reveal phenotypic characteristics, health conditions, or hereditary predispositions.
Furthermore, it determined that these materials should be collected in a non-invasive manner, using a buccal swab in a controlled environment and under technical supervision.
The (un)constitutionality of collecting genetic material in conflict with fundamental rights.
Legal factual context
The discussion regarding the constitutionality of including and maintaining the genetic profile of those convicted of violent or heinous crimes in a state database is currently underway at the Supreme Federal Court under RE No. 973.837/MG – Topic 905 , with Justice Gilmar Mendes as the reporting judge. Justice Mendes also teaches at the university level, lecturing on undergraduate and postgraduate Constitutional Law at the Brazilian Institute of Teaching, Development and Research (IDP).
The specific case involves a person convicted of a sexual crime against a vulnerable individual (article 217-A of the Penal Code), who refused to provide genetic material, conduct considered a serious offense under the LEP (Law of Penal Execution), impacting the enjoyment of benefits during the execution of the sentence.
The defense's arguments regarding the unconstitutionality of the case originating from the TJ/MG (Court of Justice of Minas Gerais) maintain that the challenged provision violates the principles against self-incrimination and due process of law, both enshrined in Article 5, paragraphs LXIII and II, of the Brazilian Federal Constitution of 88.
Furthermore, it is argued that imposing compulsory DNA collection constitutes undue interference in the individual's private life, depriving them of the possibility of choosing not to cooperate in future criminal proceedings, directly violating Article 8 of the American Convention on Human Rights (Pact of San José, Costa Rica), which ensures minimum judicial guarantees in criminal proceedings.
Prosecutor André Ubaldino Pereira, representing the Public Prosecutor's Office of Minas Gerais, defended the constitutionality of the measure, arguing that it is an essential instrument in combating impunity, which, in his view, constitutes the main "root" of crime in Brazil.
To corroborate his position, he also cited the emblematic case of the so-called "Maniac of Contagem ," emphasizing that the lack of a national database of genetic profiles can represent a significant obstacle to the prompt identification of perpetrators of serial crimes.
It was also suggested that conducting a genetic test does not necessarily lead to the conviction of the suspect or accused, but it broadens the scope of investigative possibilities, providing greater certainty in identifying the presumed perpetrators of crimes.
It argues that the regulation establishes safeguards aimed at preventing the misuse of data, imposing the requirement of a court order for access to the profile database, ensuring the confidentiality of information, and mandating the disposal of biological material after the examination is performed.
Finally, he highlighted that such a measure is relevant given the current scenario, in which the Superior Courts, notably the Superior Court of Justice, repeatedly point out the fragility of traditional means of proof, such as photographic recognition and testimonial evidence, frequently compromised by false or inaccurate memories, raising criticisms regarding the epistemic reliability of judicial interpretation.
The Rapporteur, Minister Gilmar Mendes, noted that the controversy involves defining the constitutional limits to state action in the collection, processing, and use of biological data from individuals under penal custody.
Furthermore, internationally – notably within the jurisprudence of the European Court of Human Rights – the protection of genetic information is treated as an essential dimension of the fundamental right to privacy, intrinsically linked to safeguarding the dignity of the human person.
On August 7, 2025, the Brazilian Supreme Court (STF) began the trial regarding the constitutionality of the mandatory collection and storage, in the National Genetic Profile Bank, of genetic material from those convicted of violent or heinous crimes. The process is still pending a final decision, and the session was dedicated exclusively to oral arguments.
Doctrinal and jurisprudential understanding
Guilherme Souza Nucci points out that there is no unconstitutionality regarding the collection of genetic material after a final conviction. He reveals that it is a matter of legal certainty, ensuring that one person is not prosecuted in place of another, a measure aimed at preventing one of the worst possible judicial errors.
It argues that the more secure the criminal identification, the better. The State then has the possibility of investigating crimes and identifying their perpetrators with greater precision, avoiding prosecuting one individual instead of another due to flaws or inconsistencies in the collected documentation, which is frequently subject to various types of falsification.
It goes further by arguing that the collection of genetic material should be mandatory for all convicts, as a way to prevent miscarriages of justice, regardless of the severity of the crime.
It draws a comparison with everyday situations: when a security camera records a crime, the police use the images to locate the suspect; or when fingerprints are collected at the crime scene, allowing for the identification of the perpetrator.
In these cases, it's about improving the investigative system. The accused did not necessarily provide any material to incriminate themselves. The perspective for them is different: the State collected data from other sources and compared it with an already existing genetic profile.
According to Priscila Campelo, a Federal Police delegate at the time and professor of postgraduate studies at IDP , Law No. 12.654/2012 does not present any unconstitutionality regarding the compulsory collection of biological material, but rather a foundation for the maturation of the investigative activities of the judicial police. She argues that one cannot weaken or prejudge an instrument that notably contributes to the administration of justice and is consistent with constitutional guarantees.
The Superior Court of Justice holds the understanding that it is possible to order the collection of genetic material as a form of criminal identification, either during investigations to determine the authorship of the crime, or when the defendant has already been convicted of crimes of serious violence against a person or heinous crimes. (RHC n. 69127/DF, rel. Min. Felix Fischer j.26.10.16)
It is understood that the aforementioned obligation constitutes a classification, individualization, and identification procedure, merely expanding the qualification of the convict due to technological advancements, and does not constitute invasive methods of privacy. (EDcl in RHC no. 162.703/RS, rapporteur Justice Rogerio Schietti Cruz, judgment of 04/24/2023 and STJ, HC no. 879.757/GO, rapporteur Justice Sebastião Reis Junior, judgment of 08/20/2024).
In contrast, Aury Lopes Jr. warns that, historically, the accused—whether defendant or mere suspect—was treated as a simple object of proof, the "object from which the truth that underlies the inquisitorial process must be extracted." Overcoming this view, according to the author, grounds the right not to produce evidence against oneself, ensuring silence and negative self-defense.
Additionally, Eugênio Pacelli warns that creating a national database of genetic profiles of convicts could transform an innocent individual into a suspect, exceeding the limits of the rule of law and fundamental freedoms, even while acknowledging the potential investigative benefit in cases of repeated criminal activity.
Ultimately, is it possible for genetic criminal identification and investigation to coexist with fundamental rights?
All matter occupies a place in space, possessing its own extension. The same is true in the field of criminal law: every illegal act, even if committed in a concealed manner, leaves its extension in the phenomenal world, that is, traces that materialize into evidence that can be identified and valued as evidence in the context of criminal prosecution.
Forensic science, and in particular genetic analysis, is an essential tool for identifying criminal evidence, enabling not only the elucidation of the authorship of crimes, but also the exclusion of innocent people, in strict observance of the constitutional guarantees of due process of law.
It is necessary to understand that technology is progressive and constant, and that the modus operandi of crimes evolves in the same way. The use of DNA in criminal prosecution has an impact on the community regarding public safety, especially when it is based on the pursuit of the real truth.
Certainly, in the contemporary scenario, obtaining personal information constitutes a highly sensitive activity, insofar as it can give rise to frequent threats to the sphere of individual liberties and, consequently, lead to a gradual restriction of fundamental rights.
Specifically regarding criminal genetic profile databases, there is, in a way, a potential risk of violating the privacy and confidentiality of the information contained in these samples.
The challenge is to reconcile investigative efficiency with respect for fundamental rights. To achieve this, it is essential that genetic profile databases operate with absolute confidentiality, discard samples after use, have their purpose restricted to criminal investigations, and be subject to rigorous oversight.
If balanced with responsibility and transparency, the use of DNA can represent a significant advance for criminal justice, without compromising the protection of individual rights.
