Reference sample
Definition
A biological specimen taken from the patient to establish their own DNA profile. A buccal swab or EDTA blood tube. Used by the laboratory to distinguish the patient's DNA from any foreign profile on body-surface swabs.
- Common types
- Buccal swabs or EDTA blood tubes (in clinical settings). Known-location soil or plant samples (in botanical cases).
- Purpose
- Establish a baseline profile to distinguish known DNA or plant material from unknown or suspect sources.
Common questions
What's a reference sample in forensic science?+
A reference sample is a biological or botanical sample collected from a known source, such as a crime scene or a person, used to compare against other samples. In sexual assault cases, a buccal swab or blood sample from a victim establishes their DNA profile so the lab can tell apart the victim's DNA from DNA found elsewhere on the body.
Why do labs need a reference sample from the patient?+
The patient's reference sample eliminates confusion in DNA analysis. Without it, an examiner cannot distinguish between the patient's own DNA and foreign DNA from a suspect or unknown source on body-surface swabs.
How is a reference sample collected in a sexual assault kit?+
Common collection methods are a buccal swab (inside the cheek) or an EDTA blood tube. These are standard ways to capture DNA that establishes the patient's baseline genetic profile.
Related terms
- Chain of custody
- The unbroken documentary trail of who held a sealed exhibit, when, and under what seal, from the moment of collection through analysis...
- Acetolysis
- Erdtman's 1934 extraction method. The sample is treated with a 9:1 mixture of acetic anhydride and concentrated sulphuric acid, which dissolves cellulose...
- Blank control
- A sample known to contain none of the target material, processed in parallel with real exhibits to detect laboratory contamination. A positive...
- Double-swab technique
- DNA collection method in which a wet swab is applied to the wound perimeter first to rehydrate and collect biological material, followed...
- Kit shelf life
- The period during which an unused sealed SAFE kit remains usable, typically 2-5 years depending on the manufacturer and storage conditions. Expired...
- SAFE kit
- Sexual Assault Forensic Evidence kit. The standardised collection of containers and instructions used to gather biological and trace evidence from a sexual...
- Taphonomy
- The systematic modification of bone by environmental processes after death, operating over the burial or exposure interval. Includes weathering, soil staining, sun...
- Voucher specimen
- A preserved specimen formally deposited in a collection or retained in the case file as a permanent reference. In forensic entomology, the...
- Wet evidence drying
- The mandatory air-drying step for any wet biological sample before sealing. Sealing wet evidence traps moisture, promotes bacterial growth, and degrades DNA....
Explained in these topics
- Botanical Evidence Collection and PreservationA sample collected from a known location, typically the crime scene or a control site, used as a comparator against samples from suspects or unknown objects.
- The SAFE Kit: Components and Collection SequenceA biological specimen taken from the patient to establish their own DNA profile. A buccal swab or EDTA blood tube. Used by the laboratory to distinguish the pa...