Man demands source code that linked his DNA to crime

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Prosecutors in a California court believe they have the right suspect in a series of crimes, at least partly because of a forensic DNA analysis software program.

But the defendant, Billy Ray Johnson Jr., is demanding he and his lawyers be given the software’s source code so they can determine whether or not it contains errors.

That makes sense, according to the Electronic Frontier Foundation, because evidence that is used by the prosecution cannot be withheld from the defense.

The problem?

It’s a privately owned software program and the company that runs it, TrueAllele, says the code is a trade secret. The company argues its commercial interests outweigh Johnson’s interest in justice.

A court hearing is scheduled for Wednesday in a California appeals court where EFF will argue it’s unknown “exactly how TrueAllele estimates whether a person’s DNA is likely to have contributed to a mixture, including whether the code works in practice as it has been described.”

In some cases involving spyware used by the government to monitor cell telephones, the government has dropped charges rather than reveal or expose its technological secrets.

In the Johnson case, EFF pointed out “at least two other DNA matching programs have been found to have serious source code errors that could lead to false convictions.”

EFF said Senior Staff Attorney Kit Walsh “will argue that Johnson has a constitutionally protected right to inspect and challenge the evidence used to prosecute him – and that extends to the source code of the forensic software.”

The organization pointed out to the court: “The Constitution requires that defendants be given the opportunity to review, analyze, and respond to the prosecution’s evidence. Increasingly, prosecutors are relying on evidence produced by forensic software programs – marketed and distributed by private companies to law enforcement – to establish key elements of a crime, while seeking to keep the source code that determines the outputs of that forensic technology a secret.”

Withholding that evidence, the brief argues, “prevents the defendants and the public from discovering flaws in the software that send innocent people to prison or execution. Time and again, when forensic software is subjected to independent review, errors and inconsistencies are discovered that call into question its viability and suitability for use in the criminal justice system.”

Disclosure of the source code “is required by the Constitution and by the strong public interest in the integrity of court proceedings.”

There’s no exception, the brief explains, in the rules for the disclosure of evidence that allows “even privately owned forensic software course code” to be kept secret.

“When hidden software code produces the prosecution’s key forensic evidence of guilt, the defendant’s fate can be determined by a black box that the defense has no opportunity to examine or challenge.”

The brief points out forensic technology is not immune to software errors.

“Indeed, as such technology becomes more complex (as with the new generation of DNA tools) it is at risk of error just like all complex software.”

The brief points out that when similar software, STRMix, was tested, errors where detected that created “false results” in 60 of 4,500 Australian cases.

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