A Codis Success Story

A CODIS SUCCESS STORY

On a Friday afternoon in March 1989, Debbie Smith, whose husband, Robert, is a police officer, was abducted from her home by a man she had never seen before. Mrs. Smith's assailant forced her from her kitchen to the woods behind her home. He proceeded to rape her. Before leaving the scene of the crime, the rapist threatened Mrs. Smith, saying he knew where she lived and he would kill her if she ever told anyone what had happened.

The local police department developed a suspect in the case, and sent a sample of his blood, along with the evidence, to their forensic crime laboratory. A conventional serology exam excluded the suspect. However the examiner instructed the investigating officer to preserve the evidence; there was a new examination based on DNA that could possibly solve this crime sometime in the future.

Five years later, in 1994, the county where Debbie and Robert Smith resided experienced an outbreak of sexual assault and rape crimes. The police developed a suspect in this case, and sent a sample of his blood to the laboratory. The police also resubmitted the evidence from Debbie Smith's case, thinking the same subject may be responsible. This time, the laboratory performed DNA analysis. Again, the suspect was excluded. But now, the laboratory had developed a DNA profile of the man who raped Mrs. Smith.

Meanwhile, in the years since the assault on Debbie Smith, the state had undertaken developing a databank containing DNA profiles from convicted felons. As the examiners developed convicted offender profiles, they periodically searched them against unsolved cases. This summer, Debbie Smith's rapist was identified from a match against this databank. The criminal, Norman Jimmerman, was already incarcerated for abduction and robbery. He is currently serving a 161 year sentence. The District Attorney has decided to prosecute the case; Mr. Jimmerman is a two time felon and the rape of Debbie Smith will be his third strike. When informed that the man who raped her had been identified, Debbie Smith said, "I feel like a weight has been lifted from my shoulders."

This is a true story. The hit was made at the Virginia Department of Forensic Services crime laboratory, in Richmond, Virginia.

THE CODIS CONCEPT

The COmbined DNA Index System, CODIS, blends computer and DNA technologies into an effective tool for fighting violent crime. The current version of CODIS uses two indexes to generate investigative leads in crimes where biological evidence is recovered from the crime scene. The Convicted Offender index contains DNA profiles of individuals convicted of felony sex offenses (and other violent crimes). The Forensic index contains DNA profiles developed from crime scene evidence. CODIS utilizes computer software to automatically search these indexes for matching DNA profiles.

The word "index" in COmbined DNA Index Systems is not arbitrary. CODIS is a system of pointers; the database only contains information necessary for making matches. Profiles stored in CODIS contain a specimen identifier, the sponsoring laboratory's identifier, the initials (or name) of DNA personnel associated with the analysis, and the actual DNA characteristics. CODIS does not store criminal history information, case-related information, social security numbers or dates-of-birth. Matches made among profiles in the Forensic Index can link crime scenes together; possibly identifying serial offenders. Based on a match, police can coordinate separate investigations, and share leads developed independently. Matches made between the Forensic and Convicted Offender indexes ultimately provide investigators with the identity of the suspect(s).

CODIS also supports a Population file. The Population file is a database of anonymous DNA profiles used to determine the statistical significance of a match.

CODIS is designed so that forensic laboratories have control over their own data. The system has three tiers (or levels): local, state, and national (fig. 1). The forensic and convicted offender indexes, and the population file may exist at each tier.

Typically, the Local DNA Index System, or LDIS, is installed at crime laboratories operated by police departments, sheriff's offices, or state police agencies. At the local level, DNA examiners use CODIS software on the bench when sizing autoradiograms. After sizing, examiners transfer unknown subject profiles into the local forensic index, where they are searched against other unknown

subject profiles. The custodian of the local database can share this data with other CODIS labs within the state by forwarding it to the state level.

Each state participating in the CODIS program has a single State DNA Index