DNA Case Study
The National DNA Index System also referred to as NDIS was introduced October 1999 as the Federal Bureau of Investigation’s newest tool for fighting violent crime marked its 10th year anniversary containing over 6 million casework (Forensic) and Convicted Offender DNA profiles.
NDIS is the highest level in the software program called CODIS (Combined DNA Index System) that enables participating laboratories to electronically exchange and compare DNA profiles in an effort to link biologic evidence from unsolved serial crimes with other unsolved crimes or DNA profiles from repeat violent offenders.
Each week, state laboratories send DNA profiles that have been analyzed either in the state laboratory system or from local or municipal laboratories to NDIS for the weekly search. As the central repository of DNA data generated from all 50 US states, Puerto Rico, and Army Crime Laboratory, NDIS can search a casework profile generated in Rhode Island against a casework profile from Palm Beach County Laboratory in Florida or against a convicted offender sample from New York State Laboratory System in Albany.
Rhode Island’s convicted offender legislation became effective June 1998, requiring offenders convicted of capital crimes to provide a sample for offender DNA database. The legislation was further amended in 2001 and again in 2004 requiring a DNA sample (buccal sample) to be taken from all felons as does nearly all of the states requiring all felons legislation.
A buccal sample is a swab of the lining of the cheeks to obtain DNA bearing cells used as a reference sample. Before buccal samples were used, blood was commonly drawn for the same purpose.
With the database legislation in place, the Rhode Island DNA laboratory was deemed qualified under the FBI’s Quality Assurance Standards and became eligible to participate in the National Database in 2003.
In addition to providing samples for a national search, the Forensic Biology laboratory maintains the state database and is responsible for storing and searching all DNA casework profiles received as evidence from state law enforcement searching this against other evidence or casework samples, Rhode Island convicted offenders, and any other profiles in eligible for the national database.
Database matches are classified as either Offender or Forensic Hits. An offender hit is a match between the DNA profile of an unsolved casework sample and the DNA profile taken from a convicted offender. A Forensic Hit is a match between a DNA profile of an unsolved casework sample with a DNA profile of another casework specimen. The term “hit” refers to the investigatory value of the match, did the CODIS match provide valuable information to the investigation?
The following case history describes how the Rhode Island DNA Database provided a valuable investigatory tool linking crime scene evidence to a potential perpetrator. Coventry Police submitted a sexual assault case to the Forensic Biology Laboratory for analysis, February 2000. At that time, the instrumentation and methods for the very discriminating type of DNA analysis were being developed and evaluated, and only conventional serological analysis was performed. The presence of seminal fluid was identified on the vaginal swabs taken as part of a sexual assault evidence collection kit (SAECK), without offering any further information as to the source of the seminal fluid.
The National Institute of Justice (NIJ) had long recognized state laboratories would need assistance developing the tools and technology to meet the increasing demands of processing casework and offender samples.
Therefore, the Rhode Island laboratory received funding from NIJ in the form of a Backlog Reduction grant allowing this case and others to be outsourced to a private vendor laboratory. Outsourcing would not only would reduce the backlog by providing funds for cases like this to be analyzed and providing much needed DNA analysis, but would be a means to increase the number of DNA profiles in the Rhode Island State DNA Database increasing the probability of generating matching profiles.
The DNA profile generated from the February 2000 sexual assault was submitted into the RI State DNA database September 2006. In 2006, the Coventry Police investigated a breaking and entering case. There was no indication that two unrelated cases from the opposite parts of town would be linked at that time. The following sequence of events from the original breaking and entering case provides the basis for this case study:
On 10-12-06 I was contacted by an officer and asked if I could assist him with the investigation of a breaking and entering. The officer found what appeared to be blood on a bathroom sink in a house, which had been recently stripped of all the copper piping by an intruder. I performed a phenolphthalein test on the suspected reddish brown material, which resulted in a positive reaction to the test for blood. I took several samples of the suspected blood on clean sterile cotton swabs. The swabs were later air-dried. The samples were taken to the Rhode Island State Department of Health Forensic Biology Lab for analysis and entry into CODIS.
On 8-20-07 I received a match report (“hit”) linking the previously submitted Coventry B&E case with the sexual assault case submitted in 2000.
Further investigations found, in the year 2000, the victim who had just previously had sexual relations with her boyfriend, was awakened in the middle of the night by her boyfriend’s cousin and proceeded to have sex with her while she had been sleeping.
The woman called the police. The cousin denied the allegation but was taken into custody. While at the hospital a sexual assault examination was completed and evidence in the form of a SAECK sexual assault evidence collection kit (previously known as a rape kit) was collected from the victim. The suspect agreed to provide a reference sample. The SAECK from the victim and the reference sample from the suspect were turned over to the Department of Health Forensic Biology Lab.
A profile from the case was entered in CODIS. Various items of evidence were also brought to the lab to have them entered into CODIS such as sheets and clothing. . This sample was submitted to the RI State DNA Database in 2006 as previously mentioned. Even though the case history listed a possible suspect, this sample would still be added to the state database because it was categorized as a forensic sample and the possibility exists this sample could “hit” or match with another unsolved forensic case.
Shortly after the sexual assault casework sample was added to the state database, forensic evidence recovered from the B&E case was submitted. The analysis produced a DNA profile, and even though a suspect was identified, as before, the evidence was categorized as a forensic sample and the profile was eligible for addition to the state database in May 2007. Several days later, a state search was conducted on all the new profiles against the existing profiles resulting in the B&E matching the sexual assault case.
A database match report was sent to the investigator a month later linking the two cases. Based upon the database report the investigator was able to develop a suspect and submitted the suspect’s reference sample demonstrating the suspect DNA profile matched the profiles of the two previous cases.
The following excerpt recounts the sequence of events from the original case: Because there were two males involved in the incident from the year 2000, I was asked by the Forensic Biology unit to obtain a buccal sample, from at least one of the males involved. The buccal sample serves as a reference. The DNA profile obtained from that sample will either include the suspect as the perpetrator of the offense or exclude him.
On 8-23-07, a detective was able to locate one of the males, the boyfriend of the victim in the 2000 case, and he agreed to donate a buccal sample.
I took the buccal sample and allowed it to air-dry. It was then taken to the Department of Health Forensic Biology Lab. On 1-24-08 I was contacted by the lab and advised that the buccal sample from the boyfriend in the 2000 case matched the donor of the blood on the sink in the 2006 breaking and entering case.
What does the match mean? The DNA profile from the perpetrator of the sexual assault matched the individual who left the blood on the sink following the break-in and matched the reference sample. The statistical calculation provided significance to the match. The official statement reports the statistic as the probability of randomly selecting an unrelated individual exhibiting the same profile as the evidence is 1 in 4.7 X 10 16 for a US Caucasian. This translates to the odds of finding only one unrelated individual in a group of 47,000,000,000,000,000 US Caucasians having that particular DNA profile. Clearly this DNA profile is distinctive and can unmistakably be distinguished from another profile.
The use of DNA as a tool identified the perpetrator of the B&E who was actually the consensual partner of the sexual assault victim from six years before.
If it is possible in cases of sexual assault when a victim reports consensual activity prior to or following an alleged sexual assault, an elimination sample should be obtained in order to distinguish the consensual profile from the profile of the perpetrator. However in this case, the elimination sample could not be obtained prior to the case being outsourced for analysis, and it was the matching of the two forensic profiles that generated the Forensic Hit, initiating the investigatory lead for the investigator. The victim’s boyfriend in the 2000 case was charged with the 2006 breaking and entering. He later pled guilty to the breaking and entering. Submitted by Det. Paul Koczwanski M.S. Coventry Police Department BCI Unit Robin Smith M.S. Director of Forensic Biology RI Dept.of Health Karen Lynch M.S. Principle Forensic Scientist /CODIS Administrator
|