Sperm detection can be an important factor in confirming sexual assault in cases of rape. A large number of cases received in a forensic laboratory involve sexual offenses, making it necessary to examine exhibits for the presence of seminal stains. The objective of this paper is to provide an overview of the most important methods and tests used in the identification of spermatozoa or constituents of seminal fluid during the investigation of alleged sexual assault cases in forensic medical practice. Furthermore, this paper focusses on the basic knowledge that is necessary to the graduate students who wish to specialize in forensic sciences.
ASTM International The kit is normally used by Forensic detection semen experts to collect samples from the body of the victim. No notes for slide. We use your LinkedIn profile and activity data to personalize ads and to show you more relevant seken. The chances of successful Purdue diaper of sperm depends on how long after the assault a sample is analyzed. Click here to Join the Community. It should be carried out whenever a presumptive test gives a positive result. Science Buddies. Blood is composed of liquid plasma and serum with solid components consisting of red blood cells erythrocyteswhite blood cells leukocytesand platelets thrombocytes. Any injuries sustained as a result of the assault Forrensic also be documented, described and photographed.
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If you agree to accept these cookies, confirm by clicking the Forensif, I Agree" button. Forensic Science in North Carolina. Sorry, Forensic detection semen blog cannot share posts by email. If you have questions about how or why evidence was collected at a Vintage video clips scene or the NCSCL's policies on what evidence the lab will examine, this guide may provide information. A positive result rapidly turns the test strip bright purple. An average male ejaculate measures around 3. August 06, Article. Skip to content. Precautions: Appropriate negative controls must be run as false positives are possible, especially with Type B blood. Semen Detection Test.
First, the biological facts about semen:.
- Get accurate semen test results with this kit which tests for two different substances in semen.
- In semen analysis, an alternative lights source like a laser is used to find stains on bed sheets or clothing.
- The impact of modern scientific methods on the analysis of crime scene evidence has dramatically changed many forensic sub-specialties.
- We've launched our new website at forensicresources.
- First, the biological facts about semen:.
First, the biological facts about semen:. Seminal fluid is a complex mixture of secretions from at least four male urogenital glands. An average male ejaculate measures around 3. Each milliliter can contain between 10 and 50 million sperm cells.
This number can vary with the age of the male, and can be negatively impacted by medical conditions, genetic background, diet, and other habits such as smoking and illicit drug use. Some males in the population have a condition known as oligospermia, which defines an abnormally low sperm count. Aspermia refers to another condition where the affected male produces no sperm.
Deficient sperm production may be affected by factors such as radiation and other environmental toxins, undescended testis, varicocele, trauma, drug effects or other factors. Randine Lewis, Ph. Vasectomy, which is a surgical sterilization option, renders the male incapable of producing sperm somewhere between two and four months following that procedure. Pamela J. Vasectomized, oligospermic, and aspermiac males can still produce normal amounts of seminal fluid containing both prostate gland and seminal vesicle secretions which are detectable by forensic laboratory tests as described below.
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.
Although this color pattern seems quite unique and may render sperm cells easily distinguishable under a microscope, sperm cells tend to deteriorate quickly after ejaculation.
ASTM International The sperm tails are most susceptible to damage and will break down first. Therefore, the analyst must be trained to make visual distinctions between sperm heads and other types of cells in the mix, particularly mucosal or epithelial cells whose nuclei will also stain red. Once ejected from the body, sperm survival will depend on the surrounding environment and type of surface.
It has been shown that intact sperm sperm that retains the cap and tail sections can be recovered from a vaginal cavity for a period of time following intercourse.
That time will depend on many physiologic factors. Intact sperm can also be recovered from surfaces and fabrics if the semen dried up quickly before natural breakdown occurs. Cheung, Identification of human semenogelin in membrane strip test as an alternative method for the detection of semen , Forensic Science International Similar in format to a pregnancy test strip, the RSID-semen test identifies the presence of the seminal vesicle-specific antigen, or semenogelin.
D 3, 3 This antigen is unique to semen, and therefore, there is no cross reactivity with other bodily fluids in males and females or with semen from other mammals. This test can also identify semen even if the stain was stored under less favorable conditions which have been shown to affect other tests such as the Acid Phosphatase test. Clothing, undergarments, and bedding can be quickly surveyed for potential semen stains using the naked eye.
Dried semen stains are often off-white to faint yellow in color. Under those specialized lights, semen will fluorescence due to the presence of molecules such as Flavin and Choline-conjugated proteins.
The color of this fluorescence will vary from blue to yellow, depending on the light equipment used. There are many molecules natural and artificial that will fluoresce in a similar way as semen, and therefore, this detection technique is highly presumptive. Furthermore, not all semen stains will fluoresce under such specialized lights. Exposure of the sample to factors such as heat, humidity, oxidizing agents, and microorganisms such as bacteria and mold can affect this fluorescent activity.
Semen fluorescence can also be masked by certain types of fabrics and fabric treatments. Hilton J. Kobux, D. Marshall, A. Bennett, and Dr. Using a standard chemical reaction, a forensic laboratory can analyze a given stain for the presence of this enzyme.
In the presence of Alpha-Naphthyl acid phosphate and Brentamine Fast Blue, AP will produce a dark purple color in less than a minute test is also known as the Brentamine spot test. The shade of this purple color will depend on the activity of the enzyme, which can be negatively impacted by the age of the stain and the storage conditions.
The test for AP remains highly presumptive due to the fact that vaginal secretions and other bodily fluids contain detectable levels of this enzyme. Non-semen AP enzyme reactivity is markedly slower when using the above mentioned spot test, owing to the fact that not all AP enzymes in the body are equal in their activity level.
AP activity has been detected in dried samples years after the stain was deposited. However, moisture and heat will result in the breakdown of AP in a matter of days.
Analyses of post-coital vaginal swabs show that AP activity will markedly decrease after 24 hours and diminish after 48 hours. This test was previously used by the SBI lab, but is no longer used.
PSA is produced in high amounts by the male prostate gland. However, this antigen can also be found in very small amounts in fecal material and sweat. Studies have shown PSA can also exist in female urine and breast milk. A recent study identified that the majority of women have a glandular structure surrounding the urethra that is similar to the male prostate gland.
This structure was shown to produce PSA in detectable amounts. While the PSA test remains a strong test for the presence of male semen, caution is always urged when interpreting positive PSA results which are not confirmed by the actual presence of sperm.
Dale L. Laux, M. Additional notes on pre-ejaculation fluid:. In the absence of full male ejaculation, what is the forensic significance of this fluid? It is widely accepted that pre-ejaculation fluid can contain traces of acid phosphatase and prostate specific antigen; although no evidence for the semen specific antigen semenogelin has been found to date.
There is still debate on whether sperm is expected to be present in pre-ejaculation fluid. Most scientists agree that the presence of sperm will depend on the individual male, and that pre-ejaculate sperm can be attributed to previous full ejaculation in that male.
Stephen R. Filed under Bodily Fluids. Great post, Sarah. This would be a crucial statistic! Coming from an infrared background, I struggle to find much information on absorption signature of semen and other body fluids.
Most of the work seem to be focused around the visible spectrum. I would like to know if forensic tests can determine how Old sperm is.
Most men over 50 have to get their blood tested for PSA levels. Also, there is another screening method for sperm which is much more sensitive and specific than Christmas Tree. Sperm Hy-liter is an immuno fluorescence stain that detects human sperm heads and can differentiate the sperm from all other non-specific nuclei.
You are commenting using your WordPress. You are commenting using your Google account. You are commenting using your Twitter account. You are commenting using your Facebook account. Notify me of new comments via email. Notify me of new posts via email. Sign me up! Forensic Science in North Carolina. Skip to content. Home About. By Maher Noureddine, Ph. Confirmatory Tests for semen: 1- The Christmas Tree Stain : The most reliable confirmation for the presence of semen is the positive visual identification of sperm cells or spermatozoa using the Christmas tree stain.
Like this: Like Loading October 19, at pm. This was very useful for me. It really helped me understand this type of testimony. Paul Herzog Fayetteville. May 25, at pm. Lingegowda N. September 22, at am. October 24, at am. Kathryn Marygold-Small. January 13, at pm. Dina Mattes. September 14, at pm. Leave a Reply Cancel reply Enter your comment here Fill in your details below or click an icon to log in:. Email required Address never made public.
You are commenting using your WordPress. January 13, at pm. In forensic science, presumptive tests can do two things: they either exclude a substance from being semen or confirm with a good probability that the substance is semen. No two individuals can have the same exact DNA profile with the exception of monozygotic twins. Inside the kit, one finds slides, swabs, white sheets, plastic bags and other items which can be used to store, analyze or preserve samples of semen, body fluids or hairs. In the presence of Alpha-Naphthyl acid phosphate and Brentamine Fast Blue, AP will produce a dark purple color in less than a minute test is also known as the Brentamine spot test.
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Once seminal fluid has been identified on sexual assault evidence, the DNA analyst must attempt to determine not only whether sperm are present, but which item of evidence or swab has the most sperm, in order to identify the sample most likely to provide a DNA profile. Here again, the forensic methods involved are unchanged for forty years, and current forensic identification of sperm uses a generalized cell staining method coupled with brightfield microscopy.
In theory, this should be sufficient to identify sperm, in practice sperm isolated from sexual assault evidence has lost many, if not all, of its distinctive sub-cellular organelles upon which morphological identification depends. Hence, DNA analysts spend many hours searching for sperm using a less than optimal microscopic technique.
The kit incorporates a second fluorescent dye, 4',6-diamidinophenylindole DAPI that will stain all cell nuclei; this is a fluorescent analogue of the KPIC stain currently used in most DNA forensic laboratories. The incorporation of both DAPI and Alexa dyes was designed for image processing software such that sperm recognition could be essentially automated. Only those features that have both DAPI from the DNA and the Alexa from the monoclonal antibody fluorescence would be scored by the software as sperm.
The addition of phase contrast to the method, although not required, gives less experienced crime laboratory personnel the ability to visualize cells, nuclei, and sperm in one image. Final magnification: X. These types of slides are notoriously difficult for crime laboratory personnel to analyze for the presence of sperm, as the cell density, collection method, and storage conditions all conspire to destroy sperm cell morphology and inhibit KPIC staining, making standard sperm identification methods all but impossible.
The series of images demonstrate the complexity of the original slides see phase contrast image , the ability to detect sperm in the preparation see combined phase and FITC image , as well as confirmatory steps in the process where both epithelial and sperm cells can be simultaneously identified see combined dual cube and phase contrast image.
Note air bubble at top of image. The job of the forensic analyst often involves screening many items of evidence in a case.
In semen analysis, an alternative lights source like a laser is used to find stains on bed sheets or clothing. Once a stain is found it is sent to be tested to determine the type of biological fluid it is. If the biological fluid is not blood the other options are saliva, urine or semen.
DNA profiling starts from the identification of a stain as seminal fluid. Once this is determined it is important for the DNA analyst to determine if sperm is present in the fluid. Once it has been determined that sperm is present, the analyst must determine which item of evidence or swab sample has the most sperm so that getting a DNA profile is more likely.
Forensic semen analysis
Forensic serology is the detection, identification, classification, and study of various bodily fluids such as blood , semen , saliva , urine , breast milk , vomit , fecal matter and perspiration , and their relationship to a crime scene.
A forensic serologist may also be involved in DNA analysis and bloodstain pattern analysis. Following the presumptive tests, are the confirmatory tests that confirms what the unknown substance actually is. Blood is composed of liquid plasma and serum with solid components consisting of red blood cells erythrocytes , white blood cells leukocytes , and platelets thrombocytes.
The most publicized test by crime shows is the Luminol process in which a chemical is sprayed onto a surface where blood is suspected to be. Another common presumptive test is the Kastle-Meyer or Phenolphthalein test. This is a catalytic test that detects the heme group in blood that transports oxygen and carbon dioxide.
It is a two step reaction where one drop of phenolphthalein reagent is added to the suspected blood sample, followed by a drop of hydrogen peroxide. For confirmatory tests, the Takayama Crystal Assay or an immunochromatographic test are typically used. The Takayama Crystal Assay, which forms a ferro protoporphyrin ring by a reaction between pyridine and the iron atom of the heme group. The slide is dried at degrees Celsius following the addition of the Takayama reagent. Then it is placed under a microscope and a positive result is the visualization of dark red, feathery crystals.
A positive result of this test is a color change to dark purple. For the Christmas Tree Stain, the sample is extracted with sterile water in order to make a wet mount on a microscope slide. The sample is then heat-fixed to the slide and stained with Nuclear Fast Red for 15 minutes, then rinsed with deionized water. The slide is placed under a compound light microscope for sperm observation.
If sperm are present, the heads will stain red and the mid-piece and tail stain green. If a male is aspermic or oligospermic, they either have no sperm or a low sperm count. Vasectomized males will not release sperm either. PSA p30 is a known as a prostate-specific antigen that is produced by the prostatic gland in males. This test functions similar to a pregnancy test, where if the antigen p30 is present a band will appear at the test site and a control band will appear to confirm if the test is working properly.
From there an analyst could continue to develop a DNA profile with downstream applications. The presumptive test to detect saliva is the alpha-amylase test also known as the Phadebas Test.
Using a petri dish gel, the saliva sample is added and allowed to diffuse through the gel overnight. Visualization is accomplished by adding iodine to the gel which stains the starch in the gel blue. If saliva is present, then the alpha-amylase breaks down the starch, creating a clear colored circle around where the sample was placed. For confirmatory tests there has not been as much research done compared to blood and semen.
However, RSID test have been made in order to detect alpha-amylase, but they are not always reliable because there can be a lot of false positives. Testing for different body fluids with traditional serological techniques, such as those listed above, is possible, but not without some drawbacks. Firstly, not all body fluids have a reliable confirmatory test, and those that do typically require a larger amount of the suspected stain in order to perform the confirmatory test.
This can be limiting if the forensic sample being tested is small to begin with. Also, serology is often done before any downstream analyses like DNA, so if sample is limited in size to begin with performing serological analyses and obtaining a DNA profile successfully may not be possible. Currently, researchers are looking into ways to identify bodily fluids with more success and less sample needed, and an emerging way to do this is with micro RNAs.
Given their regulatory role, the theory is that different miRNAs would be present in different amounts in certain fluid or tissue types because each of those tissue types should have unique proteins and mRNA based on their role in the body. MiRNAs are also an ideal target for forensic analysis because they are small compared to other cellular components, so they tend to resist degradation better than other tissue markers, which is important considering that case work samples are not always going to be in pristine condition .
Finally, miRNAs have the potential to be co-extracted and analyzed at the same time as DNA, combining the two processes into one for biological sample analysis, saving time and sample. Ideally, like the QIAmp kit, the extraction method used is able to extract DNA and miRNA simultaneously, minimizing the amount of reactions and the amount of sample used. However, primers and probes would have to be designed for the miRNA targets in order to do so.
The final output is an electropherogram that contains not only the STR profile of the sample, but also a peak representing which miRNA is present in that sample . Current potential miRNA biomarkers: Research is still needed in order to narrow down potential biomarkers, as some tissues and fluids have the same miRNA expressed in different concentrations. To date, blood and semen miRNAs have been the most studied and have found promising candidate biomarkers. From Wikipedia, the free encyclopedia.
Becker P. Houck, Jay A. Siegel p. Retrieved Forensic DNA Typing. USA: Academic Press. Science Buddies. August Department of Justice. Micro-rna- a potential for forensic science. Forensic Science International. Journal of Forensic Sciences. Identification of forensically relevant body fluids using a panel of differentially expressed microRNAs. Analytical Biochemistry. Categories : Forensic disciplines Crime biography stubs. Hidden categories: All stub articles. Namespaces Article Talk. Views Read Edit View history.