Since the development of the first DNA identification analyses by Sir Alex Jeffreys in 1985, DNA analysis remains widely used in law enforcement today. This is because the repetition of DNA sequences varies from person to person, demonstrating the specificity of everyone [1] . Forensic DNA analysis is solicited in several cases, such as parentage tests and human identification in forensics (human remains, clear or incriminate a suspect, etc.) from a biological sample containing DNA [2] - [4] .

Most criminal cases require the identification of a suspect from a crime scene sample through a direct comparison process (targeted or database search). Many cases require the identification of human remains, and two approaches impact the selection of the reference sample: direct and indirect comparisons.

Direct comparisons use personal objects or samples believed to be directly from the deceased, such as personal hygiene items (toothbrush, razor, contact lens, etc.) or a medical sample (blood, semen, biopsy, etc.). Indirect comparisons use a parentage or kinship approach requiring careful selection of family members. First-degree relatives (parents, children) are the most reliable choice because they are expected to share half their genome if they are related to the unidentified individual. Although identification can be supported by a single such reference sample, additional samples add statistical weight and should be collected if available [5] .

Approximately 99.9 % of the DNA sequence is thought to be identical in all humans, with only about 0.1% variation, and the probability of two non-blood related individuals having the same DNA sequence is about 1 out of 594.1 trillion individuals [6] . Forensic DNA analysis is a real tool in multiple evidence situations and remains a reference in solving forensic cases through the accurate identification of victims, and suspects in some cases [7] [8] . Since 2015, Burkina Faso faced terrorist attacks and increasing criminality. Forensic DNA analysis is not used by the Burkina Police Department during investigations because of the lack of a laboratory for forensic DNA analysis. This situation hampers the progress of investigations, the resolution of criminal cases, and human identification. Forensic DNA analysis is important to improve the identification of victims and investigations [9] . In view of the security situation in Burkina Faso, the availability of forensic DNA tests would help to identify the remains of bodies of soldiers killed on the combat front, create a database of DNA profiles of apprehended terrorists and solve justice cases. This study aimed to evaluate the contribution of forensic DNA analysis in solving criminal cases in Burkina Faso.

In this study, we were able to analyze and compare DNA profiles of biological samples from crime scenes and suspects using forensic DNA analysis. The probability of two non-blood related individuals having the same DNA sequence is about 1 in 594.1 trillion individuals [6] .

In the blast case, forensic DNA analysis established a perfect match between the victim’s DNA profile and the blood trace found at the crime scene. This match confirms that the blood trace is that of the victim and not of another person. In fact, in the case of human remains identification, it is possible to make a direct and indirect comparison. The direct approach involves comparing the deceased’s sample with a sample believed to have come from or been used by the deceased. An indirect approach uses close family members to make an identification. Both methods can provide very strong DNA evidence to support identification [5] .

In the case of the armed robbery, we determined the DNA profiles of the victim, blood trail, and suspect samples. First, we compared the DNA profile of the victim with the DNA profile of the blood trail. This first comparison was to determine who the blood trail belonged to. The comparison showed a mismatch between the two DNA profiles. Indeed, the alleles for each STR marker in the victim were different from those in the blood sample. This mismatch allowed us to conclude that the blood sample was not the victim’s but could belong to the perpetrator. Forensic investigations led to the identification of two suspects. Their genetic profile was determined and then compared to one of the blood traces. As a result, we observed a perfect match between the genetic profile of suspect n˚2 and the blood trace. This allows us to say that he would be present at the time of the crime.

In the murder case, the crime scene technicians collected biological traces at the crime scene. The analysis of these traces in the laboratory allowed the identification of another DNA profile in addition to the victim’s DNA profile. The comparison of the two DNA profiles showed a familial link between the victim’s DNA profile and the biological trace found at the scene. With the authorization of the court, a blood sample was taken from the victim’s son to compare his DNA profile with that of the biological trace. Indeed, there was a perfect match between the DNA found at the crime scene and that of the son. The son was therefore the author of his father’s murder. At a crime scene, bloodstains, semen, other biological traces, or the victim’s body are often found and each of these elements can be used as evidence. The forensic scientist then uses the evidence at hand to link the case to the arrested suspect by matching the traces to the suspect, using DNA profiling [10] . In Nigeria, in one case, there was a 100% match between the DNA recovered from the various materials found at the crime scene (rope and gloves) and the suspect’s DNA sample collected by buccal swab after the 15 STR loci were examined [4] .

Forensic DNA analysis provides evidence that can be used to convict criminals, irrefutable evidence of wrongful convictions, valuable links to actual perpetrators, and could also deter some offenders from committing more serious offenses [11] . Also, DNA has the power not only to convict the guilty, identify the dead and resolve questions of parentage but also to exonerate the innocent [9] . This means that today, DNA analysis remains a must in forensic investigations. It could be used to solve even unsolved criminal cases dating back several years. Indeed, forensic DNA analysis can be performed on human remains (bones, skeletons, skulls, etc.), tissues, etc. In this case, mitochondrial DNA would be the best choice because of its resistance. For heavily degraded samples or on hair without a bulb, it is sometimes impossible to obtain a complete profile of all microsatellites. In this case, mitochondrial DNA can be used because there are many copies of mitochondrial DNA in a cell, whereas there are rarely more than 1 or 2 copies of nuclear DNA.

Nowadays, NGS (next-generation sequencing) technology provides further innovation for highly degraded biological traces for which even extremely partial DNA profiles can be obtained [3] [12] . In addition to paternity testing and forensic DNA analysis cases, DNA fingerprints can also be used to elucidate cases such as identity theft, recognition, the establishment of civil status, maternity research, sibling research, etc. [13] [14] .

In some situations, forensic DNA analysis cannot be used as irrefutable evidence to conclude that a suspect is guilty. In these cases, the investigation should be completed with interviews of the suspect(s), neighborhood, friends, colleagues, etc., to better understand the circumstances of the crime. The facts are also other factors that can help investigators confirm the guilt or innocence of a suspect or suspects. Not every biological trace of an individual at a crime scene makes him or her the perpetrator of the crime. During crime scene investigations, technicians collect any biological trace (blood, hair, etc.) or used objects (knife, glass, cigarette butt, personal items, etc.) that may be a source of DNA [15] [16] . The goal is to not miss any evidence that could help identify perpetrators.

From all these criminal cases, we can say that forensic DNA analysis plays a crucial role in criminal investigations. It is therefore important that specialized services of the police, gendarmerie, or even centers or institutes at the national level have the human, material, and technical means to carry out DNA tests to fight against major crimes (murders, armed attacks, terrorism, etc.).

In this study, we were able to show the important role of forensic DNA analysis in the context of Burkina Faso for human identification in forensics. Indeed, any biological trace left on a crime scene is a source of DNA. It helps to advance investigations very quickly. Because of the worrying security situation, Burkina Faso should introduce forensic DNA analysis into the daily investigations of the police or the gendarmerie to facilitate investigations or the judgment of certain cases by the courts.

The authors would like to thank the Pietro Annigoni Biomolecular Research Centre CERBA/LABIOGENE) for their material and financial support in carrying out this study. We also thank Dr. François GUIDET, Expert at the Court of Aix in Provence, France, and the International Criminal Court (The Hague), and Mr. Philippe SAMAIN at Forensic France for their contribution to the enrichment of this manuscript.