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The Truth About Sex in America Today
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DNA School – Infidelity Testing

Cheating and DNA Testing to Prove It

Has your partner cheated? Do you think that you have evidence of this act?

The presence of stains on undergarments can be a possible indicator of sexual infidelity. During and after sexual activity, semen, blood and skin cells can be deposited on undergarments, panties, bed sheets, clothing, towels, upholstery or other surfaces. Sperm cells can reside in the vagina for up to five days after intercourse and can remain identifiable for years in dried stains. However, when it comes to ladies stains, you must keep in mind that many stains on female undergarments can be due to urine, urinary tract infection, blood, feces or natural vaginal excretions associated with menstruation, ovulation or vaginal infection and/or self-cleaning abilities.

Laboratory analysis of suspicious stains is performed in two stages, screening and DNA analysis.

In the first stage, the suspicious stain is manually screened by a Forensic Analyst for the presence semen or other body fluids using a series of techniques.

Secondly, we can perform a standard semen screen on any item where a stain is found. If we do confirm semen though a semen screen using a set of chemicals, there is another option beyond confirmation if there are sperm present – DNA Testing.

If we move forward with DNA Testing semen, we will perform a DNA analysis and profile that semen. (This always works best when sperm is present, otherwise we are looking for skin cells.) After we confirm a profile from the semen, we will then compare it to a reference swab from you, or the person in question, in order to determine if the semen belongs to the them or another male.

Testing semen, female or general biological stains resulting from sexual activity, which often contains a mixture of both male and female DNA. The female DNA usually originates from epithelial (skin) cells from the female’s vaginal wall, the mouth or body. Stains are first processed with a differential extraction that takes advantage of the unique characteristics of each cell type. A DNA profile is generated from each stain extract. If the male DNA in the stain does not match that of the DNA from the reference man, the results indicate that the semen stain is from another man. If it matches, then we know it’s from him.

The presence of stains on male undergarments can be a possible indicator of sexual infidelity. Natural staining of male undergarments can be caused by urine, urinary tract infection, feces or semen. Similarly, stains to undergarments from sexual infidelity with a female can be caused by semen, vaginal fluids, blood, saliva or feces.

Laboratory analysis of suspicious stains is typically performed in two stages, screening and DNA analysis.

In the first stage, the suspicious stain is screened by a Forensic Analyst for the presence semen, saliva or other biological material using a series of techniques. After screening, DNA analysis of the stain and a reference swab sample from the known partner is performed. Biological stains resulting from sexual activity often contain a mixture of both male and female DNA. The female DNA usually originates from epithelial cells from the vaginal wall, the mouth or skin. Stains are first processed with a differentia extraction that takes advantage of the unique characteristic of each cell type. A DNA profile is generated from each stain extract and from the female reference. If the female DNA in the stain does not match the DNAfrom the reference female, the results indicate the presence of another woman.

The presence of stains on male undergarments can be a possible indicator of sexual infidelity with a male. Natural staining of male undergarments can be caused by urine, urinary tract infection, feces or semen. Similarly, stains to undergarments from sexual infidelity with a male can be caused by semen, saliva, blood or feces.

Laboratory analysis of suspicious stains is typically performed in two stages, screening and DNA analysis.

In the first stage, the suspicious stain is screened by a Forensic Analyst for the presence semen, saliva or other biological fluids using a series of techniques.

After screening, DNA analysis of the stain and a reference swab sample from the known partner is performed. Biological stains from homosexual activity often contain a mixture of DNA and can originate from epithelial cells from the anus, the mouth or skin. Stains are first processed with a differential extraction that takes advantage of the unique characteristic of each cell type. A DNA profile is generated from each stain extract and from the male reference. If the male DNA in the stain does not match the DNA from the reference male, the results indicate the presence of another man.

  • Condom use often precludes the presence of semen for testing; however it may or may not eliminate foreign DNAfrom saliva or other sources.
  • Garments and other evidence samples should be placed into paper bags or envelopes and stored at room temperature. Samples should not be placed in plastic bags or refrigerated.
  • The reference sample from the known partner should be collected from the inside of the cheek using sterile swabs provided by the laboratory.

Suspicious stains can be rapidly and reliably screened for the presence of semen utilizing a combination of four techniques: ultraviolet illumination, acid phosphatase, prostate specific antigen (PSA) and microscopy.

Ultraviolet Examination

Ultraviolet (UV) light is a popular tool in many forensic investigations for the presumptive identification of body fluids on a variety of substrates. Materials such as semen, saliva, perspiration and vaginal secretions are naturally fluorescent under UV light which offers a discriminating method for locating these stains which might otherwise be invisible to the naked
eye. Once the precise location of the stain is determined, confirmatory testing can be conducted
utilizing the PSAand microscopy techniques.

Acid Phosphatase

Acid phosphatase (AP) is an enzyme secreted by the prostrate gland that is present in large
amounts in seminal fluid. AP can be found in other biological fluids, including vaginal secretions. It is therefore considered a presumptive chemical test for the presence of semen and must be confirmed by sperm detection.

Prostate Specific Antigen

Prostate-specific antigen, PSA, is a glycoprotein produced in the prostate and secreted into
seminal fluid. PSA is one of the major proteins in seminal fluid with concentrations of 0.2 to 3.0
mg/ml. In sharp contrast, PSAis found in very low concentrations in vaginal fluid, ranging from 0 to 1.25 ng/ml. This makes PSAa useful forensic marker for the detection of small amounts of seminal fluid. It can be found in the absence of spermatozoa in the case of vasectomized men. PSA
demonstrates good stability and on average is detectable in vaginal smears 27 hours after
intercourse. PSA has been recovered from semen stains as old as 30 years.

Microscopy

Sperm heads can be accurately identified based on their morphological characteristics via
microscopy.

There is a table of Typical result scenarios for semen screen

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