Semen test is a rapid test for forensic use that qualitatively detects human PSA in vaginal samples and in liquids or stains suspected of containing semen. The detection limit is 4 ng/mL PSA, and the result is read after 5 minutes.
The test can be used to examine suspected traces in connection with sexual offences or suspected infidelity. A positive result detects PSA but does not identify the person who provided the sample or prove what happened.
PSA detection and test sensitivity
What is a semen test?
The test detects PSA, or prostate-specific antigen, in a sample. PSA is a protein produced by the prostate gland and occurs in high concentrations in human semen. Small amounts may also occur in other body fluids, but the concentrations are normally considerably lower.
How sensitive is the semen test?
The monoclonal antibody test has a detection limit of 4 ng/mL PSA. It can therefore detect small PSA concentrations in a correctly prepared sample.
Samples and intended applications
According to the product information, the test can be used with vaginal samples and suspected liquid or stain samples. Sample material may be collected from underwear, bed sheets, other bedding and other materials with suspected traces.
- Vaginal sample
- Suspected liquid sample
- Dried stain
- Underwear and other textiles
- Bed sheets and other bedding
Can the test be used on dried stains?
Yes. A suspected dried stain may be used as sample material when it is prepared according to the instructions. Material collected from a textile, for example, is dissolved as instructed before the test strip is used.
Can semen be detected several weeks later?
Dried semen may, in some circumstances, still be detected several weeks after the incident. Detection is affected by the amount of sample, the material, storage conditions and any washing or cleaning. A negative result therefore does not rule out the possibility that semen was previously present on the material.
How to use the semen test
Bring the test and sample to approximately 15–30 °C. Always prepare the sample according to the instructions supplied with the product.
- Prepare the sample in a clean container.
- Remove the test strip from its protective pouch immediately before testing.
- Immerse the strip in the sample liquid for 10–15 seconds. Do not allow the liquid to rise above the MAX line.
- Remove the strip and place it on a clean, level surface.
- Read the result after 5 minutes.
How quickly is the result available?
Read the result after 5 minutes. Do not interpret the result after 10 minutes. For the best result, perform the test within one hour of preparing the sample.
Interpreting the result
Positive result
A line appears in both the control area C and the test area T. A faint T line is also interpreted as positive. PSA has been detected above the test’s detection limit.
Negative result
Only the C line appears. No T line is visible, meaning that PSA has not been detected above the detection limit.
Invalid result
The C line is absent. The result cannot be interpreted, and the test must be repeated with a new test strip.
Meaning and limitations of the result
Can the test show who the semen came from?
No. A positive result detects human PSA and suggests the presence of semen, but the test does not identify a person or link the sample to a particular individual.
Can the test prove infidelity or a sexual offence?
No. The result does not show how or when PSA came into contact with the sample, who it came from or whether sexual activity was consensual or forced. A test performed outside an official investigation does not replace professional evidence collection or forensic examination.
Storage
Store the test in its sealed pouch at 2–30 °C. Do not freeze the test or use it after the expiry date.
Important information in cases of suspected sexual offences
If rape or another sexual offence is suspected, contact the police or healthcare services as soon as possible. Where possible, avoid washing, changing clothes and handling suspected evidence before professional evidence collection has taken place.
More information about reporting a crime and the support available can be found on the Finnish Police website.
Order a semen test to examine a suspected PSA trace.
