Case History
The Need for DNA Testing to Prove Humberto Leal's Innocence of Capital Murder
In order to convict Humberto Leal of capital murder, the prosecution was required to prove that Mr. Leal kidnapped and sexually assaulted Adria Sauceda before she died—accusations Mr. Leal vehemently denies. To prove these elements, the prosecution relied on antiquated and meaningless DNA testing, and forensic "evidence" that is now universally recognized as inconclusive junk science. This evidence included the use of "luminol" to prove the presence of blood and the use of "bite mark" evidence to prove identity.
Since the state's own witnesses testified that several men had sexually assaulted Ms. Sauceda on the night of her death, the state focused on the testimony of a DNA expert and so-called "bite mark" evidence to show Mr. Leal sexually assaulted the victim.
Megan Clement, a DNA expert who testified for the prosecution, concluded that the victim was a "possible donor" of "very minute" blood spots discovered on Mr. Leal's underwear. Dr. Elizabeth Johnson, a forensic scientist, has since concluded that Ms. Clement followed deeply flawed testing protocols and provided misleading testimony. Most importantly, the outmoded technology used by Clement could not have established to any degree of certainty that Ms. Sauceda's blood was, in fact, on Mr. Leal's underwear. As the Texas Court of Criminal Appeals has since recognized, "with the science available at the time of trial in 1994, no one could credibly say that an unknown blood sample came from a given individual." Current technology, however, would permit an accurate analysis of the bloodstain in order to exclude the victim as a donor. Such a result would inevitably undercut the only rational basis for the jury's verdict. Mr. Leal has asked the state to release the evidence so that it can be subjected to modern DNA testing, yet Texas has refused.
The prosecution also produced a "bite mark expert" to testify that Mr. Leal's teeth had a unique pattern consistent with one of the bite marks found on the victim's body. The scientific community has since recognized that such bite mark comparisons are incapable of identifying an individual to the exclusion of all others. A 2009 report issued by the National Research Council of the National Academy of Sciences concluded that "different experts provide widely differing results and a high percentage of false positive matches of bite marks." Another study revealed a 63% false positive rate when attempting to use bite mark evidence to establish identity. Indeed, several men have recently been exonerated after so-called "bite mark experts" linked them to the crime. If the police investigating Ms. Sauceda's murder had taken saliva samples of the suspected bite mark, they could have performed DNA testing on the samples. Inexplicably, no samples were taken.
Finally, the prosecution claimed that luminol testing revealed the presence of blood in Mr. Leal's car—evidence they claimed was dispositive to prove that Mr. Leal kidnapped the victim. In fact, luminol reacts to substances that are not blood at all, including soils, detergents, bleaches, carpet, metal objects, tools, plastic panels, wood, and vegetable compounds. Since Luminol testing is so unreliable, and can be so misleading to the jury, courts frequently exclude the results of Luminol testing unless additional, confirmatory tests have been done to determine the presence of human blood. In Mr. Leal's case, however, no confirmatory tests were performed and defense counsel permitted the state's unfounded assertions to stand without any objections.
Current DNA technology is capable of excluding the victim as a donor to the bloodstain found on Mr. Leal's underwear. There was no other reliable forensic evidence connecting him to the offense.
