The purpose of analyzing sexual assault evidence (a rape kit) is to provide a DNA profile of the assailant. The DNA profile obtained can then be compared to the DNA profile of either a suspect or felons in a database to provide evidence that will aid the criminal justice system to apprehend and convict the perpetrator. Unfortunately, there are now an estimated:
400,000 rape kits that remain unanalyzed in forensiclaboratories in the United States, a backlog that has correctlybeen labeled a “national embarrassment”.
IFI’s proprietary technology provides a series of steps for analyzing rape kits both rapidly and accurately.
To appreciate IFI’s technology one must recognize what a rape kit is and what problems are faced in performing its analysis by a crime laboratory. The rape kit contains swabs from the victim’s body as well as relevant articles of clothing, e.g. underwear, pants, and sheets, etc. from the crime scene. What the forensic lab seeks are items of evidence containing cells from the perpetrator that will disclose his DNA profile.
Although swabs and clothing taken from the victim obviously contain cells from the victim and possibly others, it is hoped that within the evidence are cells from the perpetrator. As a sexual assault is being analyzed, sperm cells found in this evidence will almost certainly be from the perpetrator and a source of his DNA.
The first goal of the analyst is therefore to identify items of evidence in the rape kit most likely to contain sperm cells; in other words items in the rape kit must be screened rapidly and thoroughly to find those likely to contain sperm.
IFI Test Kits
A valuable way to screen evidence for the presence of sperm cells is based on IFI’s test kit,RSID™ for semen. Sperm, of course, will only be present when semen is present and the IFI test that produces a red color from a stain containing semen provides a rapid and reliable method to detect even very tiny amounts of human semen. IFI’s sensitive and specific test for human semen enables the crime lab to select quickly for further examination items of evidence most likely to contain sperm cells.
A specimen containing semen is then examined further under a high-powered microscope to search for the presence of sperm and to determine whether there are enough sperm cells to harvest for determining a DNA profile. Older methods for locating sperm are difficult for the crime laboratory because sperm cells are much smaller than other human cells (much smaller than skin cells for instance) and also easily lose their characteristic “tadpole” appearance making them difficult to identify and count under a microscope.
IFI’s SPERM HY-LITER™ (Described more fully elsewhere on this website), causes sperm cells to glow bright green under a special light source, allowing sperm in sexual assault evidence to be identified in a matter of minutes, compared to hours using older, more traditional methods. SPERM HY-LITER™ specificity is based on a special antibody that recognizes human sperm unambiguously so that such cells may be quickly found under the microscope.
The time savings using this kit can exceed 80% - and since a sperm antibody identification is precise, there is an excellent chance of identifying the best item of evidence from which to obtain a DNA profile of the perpetrator.
SPERM HY-LITER™ virtually eliminates the problem of locating sperm cells, which would otherwise be hidden by the overwhelming number of the victim’s larger skin cells.
When used together these two IFI kits reduce the time required to screen and locate sperm from sexual assault evidence from hours to a few minutes; these tests also confirm that the cells seen under the microscope are actually sperm. Thus, IFI’s new technology identifies the sperm and makes it easier to count and harvest them to provide a DNA profile of the perpetrator.
Once the stain, swab or other evidence with the most sperm cells is located, the sperm cells in the specimen must be separated from other cells, lest the subsequent DNA analysis be done on a mixture of DNA from both the assailant and another person (the victim) and hence not a true DNA profile of the assailant. IFI also provides several technologies to forensic laboratories for isolating a pure specimen of sperm cells once they have been highlighted under the microscope as described above.
IFI’s simplest sperm-isolating technology, best suited for laboratories with a small number of sexual assault cases, speeds up the current manual technology but also makes it more accurate, i.e., more sensitive and specific. Laboratories with a higher volume of rape kits, however, may opt for more expensive automated methods of isolating sperm to enhance the number of rape kits staff can analyze per day. IFI’s technical staff installs whatever system a laboratory considers appropriate and trains crime laboratory personnel to use their new technology. IFI technologies allow rape kit analysis throughput to be enhanced from 4- to 10-fold and therefore to greatly decrease the cost of processing rape kits while speeding up the availability of DNA evidence.
In Conclusion
DNA profiling has become a powerful method to identify assailants when there is no known suspect and is particularly valuable to identify repeat offenders (Undetected Rapist).
In addition, DNA evidence from sexual assaults can be used to overturn wrongful convictions for rape (Wrongful Convictions). Thus, DNA evidence has become the most important part of many forensic cases and the gold standard for a rape conviction, which should become readily available within the criminal justice system.