We've all been taught that in order for the state to get a criminal conviction, the prosecution must prove the defendant's guilt in court instead of the defendant proving his or her innocence. But in certain situations, the defendant does have an obligation to prove his or her innocence, like whenever he or she mounts what is known as an affirmative defense.
An affirmative defense is a set of facts presented by a defendant that overrides his or her conduct which otherwise might be unlawful (such as showing that the shooting of another person was in self-defense). However, the defendant's version of his or her story can be challenged by the prosecution - much like the defense can contest the state's evidence or theory of the crime.
As you might imagine, one valuable type of evidence in building an affirmative defense would be one or more witnesses who can corroborate the defendant's version of what happened. But not only can the state cross-examine these witnesses, it can also argue that a witness who could have testified but did not do so may have given testimony which would have been unfavorable to the defense. This argument is often called the missing witness doctrine.
A recent Washington Supreme Court case involved both of these legal concepts. Cory Sundberg was charged with possession of methamphetamine after police found a packet of meth in the work overalls that Sundberg was wearing when he was being arrested. At trial, Sundberg claimed that the drugs did not belong to him but were instead put there by Paul Wood, a man who Sundberg says had worn the same overalls on multiple occasions in the previous several days.
In this case, Sundberg was raising an affirmative defense that the drugs belonged to someone else; and by law, he had to prove his case on the “preponderance of the evidence” standard, which is lower than the “reasonable doubt” standard that prosecutors must meet to get a conviction. However, Sundberg testified that he didn't know much about Wood nor why he wasn't present on the day of Sundberg's arrest.
As a result, the district attorney during closing arguments “asked” the jury why Wood wasn't there to testify – and even implied that Wood didn't exist at all. Sundberg objected, alleging prosecutorial misconduct by trying to improperly influence the jury, but the DA claimed his statements were backstopped by the missing witness doctrine.
After Sundberg was convicted, he appealed his decision to the state appellate court, who actually agreed with his argument and overturned his conviction. However, in the State v. Sundberg decision which was released last week, the Washington Supreme Court reversed the appeals court ruling and declared that no misconduct took place, writing "a prosecutor can question a defendant's failure to provide corroborative evidence if the defendant testified about an exculpatory theory that could have been corroborated by an available witness."
In short, if you ever try to assert the oft-cited defense of “the drugs weren't mine” in court, you would best be served to have the “real” owner of the drugs corroborate your story on the witness stand; otherwise, the prosecutor can claim to the jury that you're lying.