Forensics

  • Forensic Sperm Detection
  • Forensic Histopathology

Forensic scientists are tasked with the collection, preservation, and analysis of scientific evidence during the course of a criminal investigation. Within the field of forensic sciences, detection of semen is the primary method to confirm sexual assault. Other evidence, such as tissue samples, is used to examine the nature of incidents that may have been the cause of a person’s death.

Forensic Sperm Detection

Separation of sperm cells from the victim's DNA is crucial for identifying and characterizing the perpetrator's DNA profile. New methods to separate spermatozoa from other cells (e.g., with a laser microdissection system like the PALM MicroBeam system from Carl Zeiss) increase the efficiency of the method. However, in forensic samples the overall number of spermatozoa can be very low, and there usually is a very inhomogeneous background of debris and other cells. Thus, traditional visual methods to detect sperm remains are limiting cases turnover and are often causing backlogs.

Automation of sperm detection is an efficient method to solve sexual assault crimes more efficiently. With Neon Metafer sperm cells in forensic samples are automatically detected, and their positions on the slides are stored. Coordinates of objects can be immediately transferred to a microdissection system.

The most reliable confirmation for the presence of semen is the positive visual identification of spermatozoa using the so-called Christmas Tree staining method. Two main reagents are used consecutively to produce this distinctive stain: Picroindigocarmine stains the neck and tail portions of the sperm in green and blue, while Nuclear Fast Red (also known as Kernechtrot) gives the sperm heads a red color and the tips of the heads, an area known as acrosomal cap, a pink color. Neon Metafer finds objects showing this staining pattern, creates gallery images, and sorts them by quality.

Automated rare events detection is also available for various other protocols including dedicated fluorescence markers. Detected objects are fully documented as gallery images, and cells are linked to their respective position on the sample. Adaptable ranking data allow for fast selection of cell subgroups. Results can be easily inspected on screen or at the microscope, and unwanted objects are rejected with just a mouse click.

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Forensic Histopathology

Forensic histology or histopathology applies histological techniques to forensic pathology practice. It becomes very useful in the case of a sudden death where trauma and poisoning need to be ruled out. Microscopic examination of human tissue can yield valuable information about the nature and extent of an injury present in an individual that may be related to the cause of death. Findings can be quite significant because the examiner will pass this information on to those responsible for the criminal investigation and may also need to testify in court. This is why quick responses, the 4-eyes principle for any assessment, and a thorough documentation of the findings become very important here.

The Metafer-based, automated slide digitization system is an extremely versatile imaging toolbox offering many features helping to achieve these scopes. Samples of various origins can be fully digitized and subsequently used as basis for interpretation. Once digitized, degradation of the sample is of no importance anymore – the evidence is at hand whenever it is needed. Furthermore, it now becomes very easy to discuss over the image, to share opinions, and to develop findings.

Metafer’s outstanding flexibility provides a completely new insight into the sample. Regular brightfield light microscopy can easily be combined with fluorescence, with phase contrast, and even polarized light microscopy. Images obtained with these different methods can be superimposed, and cross-evidence can be visualized. Once elaborated, any investigation protocol can be made highly reproducible. This helps to reduce subjectivity, and to move closer towards robust QC/QA conditions.

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