top of page

The Misuse of Soluble ABO Blood Group Substance Analysis

Post-Conviction Litigation:
Why You Need Expert Review of All Conventional Serological Genetic Testing

Prior to the advent of DNA testing in the late 1980s and early 1990s, genetic discrimination of potential sources of body fluid evidence other than blood was very limited, particularly in sexual assault cases, to the detection of soluble ABO blood group substances and a few polymorphic enzymes that occur naturally in semen, saliva, and vaginal fluid. This physical evidence generally consisted of body orifice, external genital, and skin swabs, stains on various garments, bedding, and other fabrics, condoms and feminine hygiene products, and pubic hair specimens. Usually, the evidentiary body fluid - semen, for example - was commingled with body fluids from the victim. Without some objective quantification of the amount of semen present forensic analysts could not be certain whether any detected genetic traits arose from the semen. Hence, only genetic traits foreign to the victim could be attributed to the semen. The detection of soluble ABO blood group substances is further complicated by the fact that not everyone reflects, or secretes, their ABO blood type in soluble form in their other body fluids.

The table below shows the antigens secreted and approximate population frequencies for the ABO blood system.

ABO Phenotype Table crop_edited_edited.jpg

The Infamous Prosecution and Exoneration of Gary Dotson

Gary Dotson was the first falsely convicted person in the US to be exonerated with DNA analysis. For a detailed account of his entire saga, click here. In summary, in 1977 Dotson was charged with rape in Illinois. An Illinois State Police criminalist testified the semen in the crotch of the victim's panties originated from a B secretor and that B secretors comprised approximately 10% of the Caucasian population, including Dotson. This evidence, along with the victim's identification convinced the jury that Dotson's alibi was contrived and he was convicted in 1979 and sentenced to 25 to 50 years in prison. The fact that the victim was also a B secretor, although known, was not revealed by the state criminalist. Also, the state criminalist had made no effort to estimate the concentration of the semen in his mixed sample from the panties. These undisclosed facts reveal the victim could be the source of some or all of the B blood group substance detected in sample. This means that the semen donor could be a B secretor, an O secretor, or a non-secretor. Even worse, in the absence of any objective determination indicating the semen was sufficiently concentrated that one would expect to detect soluble blood group substance from the semen, no genetic information may be inferred about the semen donor - no one could be eliminated by the test result. The very first exoneration effected by post-conviction DNA testing is a prime example of misuse of conventional serological testing all across the US.

The table below summarizes the possible conclusions from the Dotson case testing.

ABO B example.jpg

Inappropriate Interpretation and Testimony of Soluble ABO Blood Group Evidence was Common and Widespread

The Innocence Project lists 58 exonerations in which flawed conventional serological testing contributed to convictions. In 2009 Garrett and Neufeld reviewed the trial transcripts in 100 exoneration cases with forensic serology testimony and determined that the testimony was invalid in 57%. The National Registry of Exonerations lists 745 of 3,249 exonerations of which False or Misleading Forensic Evidence was a contributing cause of the conviction and DNA analysis contributed to 245 exonerations. As was revealed by the 2022 review and subsequent exoneration of Sullivan Walter (see here), law enforcement analysts across the country made the same ABO testing interpretive errors and gave flawed testimony - likely over and over while the procedure was in use. Often, analysts testified the ABO findings "matched" the defendant when in fact no genetic traits foreign to the victim were detected. Many of these cases have been discovered during post-conviction DNA testing.


The National Registry of Exonerations lists 52 cases out of Illinois dating back to 1978 in which false or misleading forensic evidence contributed to conviction, 31 of which DNA testing contributed to the exonerations. The chronic misuse of conventional serological testing by a law enforcement agency is exemplified by the now defunct Chicago Police Department crime lab. Expert peer review has revealed concealed exculpatory serological evidence, flawed testing, and inappropriate ABO testimony in case after case to the extent the CPD lab was shut down/taken over by the Illinois State Police (which as the Dotson case shows was not immune to similar failures.) In many of these cases, the flawed testing and false reporting could have been discovered pre-trial by mere peer review of the laboratory case file - which did not happen in the CPD lab or by the defense. These cases go back to 1978 and include Ronald Jones, John Willis, Omar Saunders et al, Kenneth Adams et al ("the Ford Heights Four"), Larry Gillard, Bennie Starks, and many more. The City of Chicago and Cook County have paid hundreds of millions of dollars in civil suits as the direct result of improper conventional serological testing contributing to false convictions. The Omar Saunders et al case is highlighted below.

The False Conviction of Omar Saunders, Larry Ollins, and Calvin Ollins

In 1986 Lori Roscetti, a 23 year old medical school student in Chicago, was raped and murdered. Four local boys: Omar Saunders 18, Larry Ollins 17, Calvin Ollins 14, and Marcellius Bradford were arrested. Calvin confessed having been told he could then go home. Bradford agreed to testify against Larry, plead guilty, was sentenced to 12 years, and was released after serving 6 years. Saunders, Larry, and Calvin were convicted as adults in separate trials in 1988 and all sentenced to life in prison - Calvin without possibility of parole. At sentencing the judge stated he would have sentenced Larry to death if possible. 


The Chicago Police Crime lab determined semen was present on the victim's vaginal swabs. The victim was determined to be a non-secretor. H blood group substance was detected on the vaginal swabs, indicating the presence of semen from an O secretor. Another genetic trait (the PGM 1- isozyme) foreign to the victim was also detected. CPD determined all four of the boys were non-secretors. This meant that all of the boys, alone or in any combination, were eliminated as the source of the semen. Nevertheless, the CPD criminalist testified in each trial that none of them could be eliminated - corroborating the confessions.


In 2000 I reviewed the CPD lab records, reports, and testimony and discovered the false testimony. This review included several other cases worked by the same analyst. This review revealed a pattern of misinterpretation and false testimony by the analyst. In 2001 DNA testing was conducted on several items including the vaginal swabs. All four boys were eliminated and two unique semen donor profiles were obtained. The actual assailants were identified in 2002.

The conventional serological investigation of semen evidence in the Harrell case is demonstrative of the extreme extent to which misuse of soluble ABO blood groups substance testing can be taken as false incriminating evidence. In 1988 Harrell was arrested in New Jersey for rape and he was convicted in 1992. The New Jersey State Police Crime lab analyst determined semen was present on the victim's vaginal swabs and on the inside crotch panel of the panties. Of course, the semen was necessarily commingled with vaginal fluid. Harrell and the victim were both determined to be O secretors. The NJSP analyst detected only H antigen from the vaginal swab and panties samples. His reports reflected only these facts - no conclusions were expressed and no population frequency estimates were provided. At trial the analyst testified that the source of the semen was an O secretor which included about 32% of the population. He then testified that this percentage could be further narrowed by eliminating females, pre-pubertal males, aspermic and impotent males, and finally he restricted this group to Blacks, such that only 2% of the Black virile male population, including Harrell, qualified as the source of semen. In truth, the NJSP analyst had no genetic information whatsoever about the source of the semen - no one could be eliminated based on his findings. Harrell was eliminated via DNA testing in 2016 and subsequently exonerated.

bottom of page