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Body Fluid Identification

Date Published
November 9, 2017

Sidebar to the article Sexual Assault Cases: Exploring the Importance of Non-DNA Forensic Evidence by Heather Waltke, Gerald LaPorte, Danielle Weiss, Dawn Schwarting, Minh Nguyen, and Frances Scott.

Methods used to examine sexual assault evidence — such as the use of an alternate light source (e.g., ultraviolet light) to visually detect semen stains, histological microscopic examination to observe spermatozoa, chemical methods based on the detection of seminal fluid acid phosphatase, and immunological methods based on the detection of p30 (or prostate-specific antigen) — have been described in scientific literature for more than three decades. Other common body fluids for which presumptive identification methods are routinely employed include blood and saliva. Such methods are typically based on the detection of hemoglobin (blood) through a phenolphthalein (Kastle-Meyer) test and the detection of saliva through an α-amylase test. Regardless of whether serological tests are performed as a screening step prior to DNA testing or to provide additional substantive case information after DNA testing, they are instrumental tools for forensic investigators.

Technology companies continue to develop new kits and tools to make body fluid identification more discriminatory, faster, and less labor intensive. More recent commercial advances boast the ability for multiplex testing to identify multiple body fluids simultaneously in a relatively short amount of time.

Meanwhile, NIJ continues to fund innovative research to address the need for new tools to better identify body fluids while minimizing the consumption of evidence. With NIJ funding, spectroscopic methods used in other analytical chemistry applications are being applied to forensic science to develop new methods. Attenuated total reflection (ATR) Fourier transform infrared (FT-IR) spectroscopy has the potential for nondestructive blood stain analysis in laboratory and crime scene settings.[1] Raman spectroscopy coupled with chemometrics has been shown to be able to discriminate between peripheral blood, menstrual blood, saliva, semen, sweat, and vaginal fluid, without consuming any sample.[2] Advances are also being made in surface-enhanced Raman spectroscopy for the identification of dried blood, semen, vaginal fluid, saliva, and urine.[3] NIJ funds are also being used to develop multiplex methods to identify multiple body fluids (e.g., human saliva, urine, seminal fluid, vaginal fluid, peripheral blood, and menstrual blood) using mass spectrometry.[4] As forensic laboratory interest in massively parallel sequencing technologies increases, NIJ’s investments into research projects that support sequence analysis-based methods to identify body fluids are becoming more relevant to potential practice.

Scientific methods used to identify body fluids, as currently performed or as they may be in the future, are important factors that can influence the crime scene investigation, inform the forensic laboratory processing, and affect court outcomes. Regardless of the perceived adequacy of existing methods, it is critical to continue to advance the field, building on new scientific findings and technologies that continue to evolve rapidly. As the field moves forward, it is critical to also continue to generate publicly available scientific knowledge that rigorously tests new methods, validates that the methods can do what they purport, and ultimately supports the foundation for the new tools and technologies that are adopted into practice.

About This Article

This article was published as part of NIJ Journal issue number 279, published April 2018, as a sidebar to the article Sexual Assault Cases: Exploring the Importance of Non-DNA Forensic Evidence by Heather Waltke, Gerald LaPorte, Danielle Weiss, Dawn Schwarting, Minh Nguyen, and Frances Scott.

Date Created: November 9, 2017