Forensic DNA Profiling: PCR Techniques and Innovations

Dear Colleagues,

Forensic DNA profiling has become an essential tool in modern criminal and even civil justice, offering scientific methods for identifying individuals with high accuracy using their genetic material. Central to this process is the Polymerase Chain Reaction (PCR), a molecular biology technique that amplifies tiny quantities of DNA recovered from crime scenes or other forensic contexts, making it possible to analyze. A PCR works by repeatedly copying specific DNA regions, exponentially increasing the amount of target DNA to detectable levels. Over the years, PCR-based methods have been refined with the introduction of a multiplex PCR, allowing for the simultaneous amplification of multiple loci in a single reaction. This technique is associated with capillary electrophoresis, which separates DNA fragments according to their size using a thin capillary filled with a gel-like polymer and offers a high resolution and speed. These methods improve the efficiency and discriminatory power of DNA analysis. In forensic applications, the traditional PCR genetic target regions have included the autossomal Short Tandem Repeat (STR), the Y-STR, mitochondrial DNA, autossomal Single-Nucleotide Polymorphisms (SNPs), and Y-SNPs, which have formed the backbone of forensic investigations for the last four decades. Methods employing these target regions are widely used in solving crimes, identifying missing persons, and verifying familial relationships.

In recent years, however, the field has witnessed transformative innovations. Advances such as Next-Generation Sequencing (NGS), rapid DNA technology, forensic genetic genealogy, and DNA phenotyping have significantly expanded the capabilities of forensic laboratories. Next-Generation Sequencing (NGS), also called massively parallel sequencing (MPS), allows for the sequencing of numerous DNA regions at once, providing more detailed genetic information than traditional PCR–capillary electrophoresis methods. NGS enables the simultaneous analysis of not only the STR but also Single-Nucleotide Polymorphisms (SNPs) and mitochondrial DNA, expanding laboratories’ capability to handle more complex samples. Rapid DNA technology represents another breakthrough, offering automated and portable systems capable of generating DNA profiles in under two hours. This innovation supports quick decision-making in field investigations, border control, and disaster victim identification. Forensic genetic genealogy has also emerged as a powerful tool, combining DNA analysis with large genealogical databases to identify unknown individuals by tracing their familial relationships. Finally, DNA phenotyping techniques provide the ability to infer individuals’ ancestry and physical characteristics through genetic material analysis.

PCR-based forensic DNA profiling, bolstered by modern innovations, continues to be a cornerstone of forensic science, improving both the speed and precision of criminal and civil investigations worldwide. However, despite their advantages, all of these innovations also introduce complex ethical and legal challenges, particularly in terms of privacy, data security, and consent, which must be carefully managed to maintain public trust and uphold justice.

Dr. António Amorim
Dr. Laura Mendes Cainé
Guest Editors

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• forensic DNA profiling
• PCR-based forensics
• DNA analysis
• next-generation sequencing
• short tandem repeat (STR)
• Y-STR
• single-nucleotide polymorphisms (SNPs)
• Y-SNP