A stability study on Gc subtyping in bloodstains: comparison by two different techniques

Area of Science:

• Forensic Science
• Genetics
• Biochemistry

Background:

• Gc (Group Specific Component) subtypes are important genetic markers.
• Accurate determination of Gc subtypes in bloodstains is crucial for forensic investigations.
• Existing methods for Gc subtyping in aged bloodstains have limitations.

Purpose of the Study:

• To compare the efficacy of immunofixation and sulfosalicylic acid precipitation methods for Gc subtyping in bloodstains.
• To determine the limits of determination for each method based on storage conditions and time.
• To recommend the optimal method for forensic casework.

Main Methods:

• Isoelectric focusing on polyacrylamide gel was used for both methods.
• Bloodstains were stored at different temperatures (37°C, room temperature, 4°C).
• Gc subtyping was attempted at various time points post-stain formation.

Main Results:

• Immunofixation allowed successful Gc subtyping after 7 weeks at 37°C, 17 weeks at room temperature, and 25 weeks at 4°C.
• Sulfosalicylic acid precipitation failed to determine Gc subtypes after only a few weeks of storage.
• The immunofixation method demonstrated significantly greater sensitivity and stability.

Conclusions:

• The immunofixation method is highly effective for Gc subtyping in bloodstains, even after extended storage periods.
• The sulfosalicylic acid precipitation method is unreliable for aged bloodstains.
• Immunofixation is the recommended method for Gc subtyping in medicolegal practice due to its superior performance.