Forensic serology is a specialized field within forensic science that analyses blood and other bodily fluids to aid criminal investigations. By examining these fluids, forensic scientists can provide critical evidence that links suspects, victims, and crime scenes.
This article explores the methods and applications of blood and bodily fluid analysis in forensic serology.
Blood Analysis
Introduction and Significance
Blood is crucial in many criminal investigations because it provides definitive information about an individual’s involvement in a crime. It contains DNA, blood type, and other markers that can establish links between individuals and crime scenes.
Analytical Techniques
- Presumptive Tests: The initial step in blood analysis often involves presumptive tests to detect the presence of blood. Tests such as the Kastle-Meyer test and the Luminol test are commonly used. The Kastle-Meyer test relies on the reaction between blood and phenolphthalein, which produces a pink colour if blood is present. Luminol reacts with haemoglobin in the blood, emitting a blue glow in the dark, which helps detect blood traces at crime scenes (Saini et al., 2014).
- Confirmatory Tests: Once blood is detected, confirmatory tests verify its identity. The most commonly used confirmatory test is the Hemostix test, which confirms the presence of human blood by detecting specific proteins. Blood typing can also be performed to determine blood groups, which helps match the blood sample to an individual (Gunn & Woodward, 2012).
- DNA Analysis: DNA profiling is a powerful tool in forensic serology. Polymerase Chain Reaction (PCR) and Short Tandem Repeat (STR) analysis amplify and analyze DNA from blood samples. These methods provide a high level of specificity and can match DNA from crime scene samples to potential suspects or victims (Butler, 2015).
Applications
Blood analysis is crucial in cases of violent crimes such as homicides, assaults, and sexual offences. It can establish a suspect’s presence at a crime scene or confirm a victim’s identity. Bloodstain pattern analysis, which examines blood stains' size, shape, and distribution, can also provide insights into the events during a crime.
Bodily Fluids Analysis
Introduction and Significance
In addition to blood, forensic serology involves the analysis of other bodily fluids, such as semen, saliva, and urine. Each of these fluids can provide valuable evidence in criminal investigations.
Analytical Techniques
- Semen Analysis: Semen is often analyzed in cases of sexual assault. Presumptive tests, such as the Acid Phosphatase test, detect the presence of enzymes specific to semen. Confirmatory tests, like the Christmas Tree Stain, visualize spermatozoa under a microscope, allowing forensic scientists to identify semen with high accuracy (Kurtz et al., 2006).
- Saliva Analysis: Saliva can be collected from bite marks, drinking glasses, or other items. The detection of amylase, an enzyme found in saliva, is used as a presumptive test. Confirmatory methods include DNA profiling to match saliva samples to individuals (Davis & Fortes, 2011).
- Urine Analysis: While less common, urine analysis can be helpful in some instances. Presumptive tests for urine include the use of urea or creatinine. DNA analysis can also be performed if sufficient urine volume is available.
Applications
Bodily fluids are often analyzed in cases of sexual assault, where semen can confirm the presence of the perpetrator. Saliva can link suspects to crime scenes or victims, while urine analysis may provide additional context in specific cases. Studying these fluids helps build a comprehensive picture of the events surrounding a crime.
Forensic serology encompasses the analysis of blood and other bodily fluids, providing essential evidence in criminal investigations. Forensic scientists can use various analytical techniques to identify and match biological samples, linking suspects, victims, and crime scenes. Meticulously examining these fluids is crucial in solving crimes and ensuring justice.