Translational Research Could Boost Rape Convictions

By Melissa Maki

A human sperm stained with SpermPaints. The band around the mid-region of the sperm head corresponds to staining with monoclonal antibodies to ESP while the tail is illuminated with monoclonal antibodies to the biomarker protein CABYR.

John Herr, professor of cell biology and director of the Center for Research in Contraceptive and Reproductive Health, has been concerned with characterizing sperm proteins and the testicular genes that encode them for nearly 30 years.   Fundamental discoveries made in his University of Virginia laboratory were recently translated into a product that could vastly improve the field of sexual assault forensics. 

In cases of sexual assault, often the victim is the only crime witness, making criminal charges difficult to prove.  “The identification of sperm remains among the most important pieces of evidence to corroborate victim testimony,” says Herr.  “If sperm are abundant in the evidence sample, the microscopic identification process is fairly routine.  However, if few sperm are present, the forensic practitioner may spend hours examining the evidence searching for a single cell.”

In U.S. federal and state crime labs there is currently a backlog of more than 500,000 cases of evidence waiting to be processed microscopically and by DNA fingerprinting.  In sexual assault cases, forensic lab technicians must scrutinize specimens for a single, anatomically intact cell—identified by recognition of the sperm’s characteristic, tadpole-like appearance.  Confounding sperm searches are natural processes which degrade the sperm, resulting in the separation of sperm heads and tails.  Once the head and tail have separated it is difficult to conclusively make a positive identification, especially since cells from the victim typically predominate and may mask the sperm.

With funding from the National Institute of Justice, Herr’s lab developed SpermPaints—a product that enables the rapid, microscopic detection of sperm.  Herr’s lab previously discovered, named, cloned, and patented two sperm protein biomarkers: equatorial segment protein (ESP) is located in the sperm head, in a distinctive belt-like band that crosses the mid region, while calcium-binding tyrosine phosphorylation-regulated protein (CABYR) is located in a specific region of the sperm tail called the principal piece.  SpermPaints consists of fluorescently labeled monoclonal antibodies that bind exclusively to the ESP and CABYR proteins.  “We’ve coupled the monoclonal antibodies with fluorescent tags so a forensic analyst can easily visualize sperm heads or tails under a fluorescent microscope, even if they are detached,” notes Herr.  “It’s a very distinctive way to identify the sperm head or tail as it lights them up against a black background when excited by light of a specific wavelength.”

SpermPaints could dramatically increase the ability of crime labs to process sexual assault evidence and positively detect sperm, even in samples where many hours elapse from assault to sample collection. “SpermPaints has worked on samples 96 hours after intercourse,” says Herr.  This is an important feature, since trauma, embarrassment, and fear often prevent victims from seeking immediate medical attention following an assault.  The increase in positive identifications would support victim testimony—likely resulting in an increase in the number of sexual assault convictions.

Herr anticipates that full deployment of SpermPaints to the more than 350 state and federal crime labs will require some legislative assistance.  SpermPaints requires the use of fluorescent microscopes and cameras—high-end technology that isn’t available in most crime labs.  He suggests that the DNA Analysis Backlog Reduction Act could be amended to authorize and appropriate funding for the labs to purchase the equipment at a cost of about $12,000 per lab.

SpermPaints is a prime example of what is possible with translational research—when basic science is transformed into a valuable, practical application.  Herr’s lab identified the biomarkers, envisioned an end product based on this discovery, and then developed the fluorescent probes.  Now Herr hopes to bridge the chasm between the available new product and the end user by gaining the support of federal legislators to speed deployment of the enabling microscopic technology.