The DNA Laboratory comprises three separate units, Nuclear DNA, Mitochondrial DNA and CODIS (Combined DNA Index System). Each is tasked with assisting law enforcement agencies throughout the State of New Jersey and the United States in solving crimes utilizing state of the art DNA technology.
DNA stands for Deoxyribonucleic Acid. DNA is genetic material, which stores the inherited traits that make up our bodies. The information stored in DNA gets passed on from one generation to the next. Two types of DNA are found in the cells of the body: nuclear DNA and mitochondrial DNA (mtDNA). Nuclear DNA is a linear molecule that is packaged in the form of chromosomes (humans have 23 pairs of chromosomes) and it is located within the nucleus of the cell. Half of the chromosomes are inherited from the mother and half are inherited from the father. Mitochondrial DNA is circular and it is located within small structures called mitochondria. There are hundreds of mitochondria per cell, each of which may contain several copies of mtDNA. Mitochondrial DNA is inherited only from the mother; fathers do not pass mtDNA to their children. The DNA laboratory has one unit dedicated to the analysis of nuclear DNA and another to the analysis of Mitochondrial DNA. The New Jersey State Police Office of Forensic Sciences, DNA Laboratory was chosen from public laboratories across the country by the FBI to serve as one of four regional mitochondrial DNA Labs. In addition to criminal casework, this laboratory will process samples from missing person’s cases and subsequently upload the results into a missing person’s index within the CODIS database. This will assist law enforcement agencies in bringing closure to families missing loved ones.
The Nuclear DNA Unit
The Nuclear DNA Unit receives physical evidence containing biological stains (blood, semen, or saliva) from crimes involving homicides, sexual assaults, kidnappings, aggravated assaults, and burglaries. The stains are subsequently analyzed for nuclear DNA using a four-step process: extraction, quantitation, amplification and detection. Commercially available amplification kits are used to type the 13 core loci (genetic markers) as required by the FBI’s National DNA Index System (NDIS). These 13 locations along the DNA molecule are made up of short tandem repeats (STR’s) found on 11 different chromosomes. The number of times each STR is repeated at the 13 loci constitutes a genetic profile. A genetic profile that is produced from analyzing a piece of biological evidence can be directly compared to the genetic profile of a reference control sample from either a victim or suspect. From this comparison, a scientist can conclude whether a person is included or excluded as the source of the stain. Profiles from evidentiary items can also be uploaded to the CODIS database and searched against other unknown forensic profiles and convicted offender profiles – a powerful tool when a crime occurs and there are no leads to a possible suspect. When a forensic unknown profile matches the profile of a reference sample, a scientist performs a statistical evaluation to give weight to this match. Typically the chance of selecting a randomly chosen individual that matches at all 13 loci is less than 1 in a quadrillion. A quadrillion is 1 followed by 15 zeroes. In addition to writing reports, DNA scientists are often called to court to testify as to the results and conclusions of their analyses.
In the past few years, the NJSP DNA Laboratory has increased the size of its staff and instrumentation in order to keep up with new developments in the field. As part of the new developments, the Nuclear DNA Unit now has the capability to analyze biological evidence for Y-STR's. Y-STR analysis is specific to the Y chromosome, and targets only male DNA, invaluable when a mixture of female and male DNA is present (e.g., sexual assault cases). While this can be a very useful tool, the Y-STR profile and resulting statistics are not as discriminatory as those typically found in a 13-core loci match. This is due to the fact that all paternally related male individuals share the same Y-STR profile. An individual who does not match the Y-STR profile can be positively excluded as the source of the Y-STR profile. However, when a person matches the Y-STR profile he is included with a host of individuals that may have this same profile.
The Mitochondrial DNA Unit
The Mitochondrial DNA Unit began analyzing biological samples for mitochondrial DNA (mtDNA) in the fall of 2005. Two general categories of casework are accepted: criminal and missing persons/unidentified human remains. Typically, mtDNA analysis is utilized for those specimens where the quality and/or quantity of DNA are insufficient for nuclear DNA analysis (e.g., hair, bones, and teeth). Mitochondrial DNA analysis is also utilized in cases where maternal relatives are the only available reference source.
Advantages of mtDNA
Because of it’s structure, location, and high copy # within the cell, mtDNA is much more robust than nuclear DNA and is more likely to be found in old, degraded and environmentally damaged samples. Mitochondrial DNA is also more likely to be found in samples that contain very little nuclear DNA to begin with, such as hair shafts, bones and teeth.
Because mtDNA is passed on from mother to child, all maternal relatives are expected to share the same mtDNA profile. This characteristic is advantageous because sometimes the proper reference samples needed for nuclear DNA comparison are not available (e.g., missing persons or mass disasters). In these situations, any maternal relative may be used for comparison purposes.
Suitability of mtDNA Analysis
Because nuclear DNA analysis is more discriminating than mtDNA analysis and has the potential for identifying the source of the DNA, nuclear DNA analysis is usually the preferred method of testing. However, when items of evidence contain little or no nuclear DNA, or proper reference samples aren’t available to compare to the evidence, mtDNA analysis becomes a powerful investigative tool. The results can provide an important link between victim, suspect, and /or crime scene and can also conclusively exclude an individual as being the source of a mtDNA profile.
The majority of cases in which mtDNA analysis is performed involve hair evidence where only the hair shaft is present. Mitochondrial DNA analysis is also justified for hair evidence where no tissue is present on the root. A hair examination needs to be performed prior to mtDNA analysis to determine that the hair is human, its suitability for comparison to known reference hairs, and its suitability for nuclear DNA analysis. In addition, other identifying characteristics such as race and body area may be determined through a hair examination.
Mitochondrial DNA analysis in unidentified remains cases is appropriate only when a forensic anthropologist and/or forensic odontologist can verify bone or teeth specimens as of human origin. During the examination, the best specimens for DNA analysis will be selected. In addition, an anthropological examination may obtain considerable information for identification and investigative purposes (e.g., sex, race, age, stature, trauma related to cause of death).
DNA analysis is a destructive process that can potentially consume the evidence. Therefore, all identifying information from hairs and human remains needs to be recorded prior to DNA testing.
Mitochondrial DNA analysis is generally not performed on questioned bloodstains unless the appropriate reference samples are unavailable for nuclear DNA analysis. Suppose that a kidnapping victim is missing but a bloodstain is found in the suspect’s vehicle and only a maternal relative’s (e.g., mother, sibling) reference sample is available for the victim. In that case, mtDNA analysis could be conducted using a portion of the vehicle bloodstain, the maternal relative’s reference sample, and the suspect’s reference sample.
Current available techniques cannot effectively distinguish between sources or relative quantities of mtDNA. Consequently, mtDNA is not appropriate for evidence containing possible mixed sources of DNA such as semen stains from sexual assaults, fingernail scrapings, clothing, and “touch DNA” such as doorknobs, steering wheels, telephone receivers, etc.
The CODIS Unit
CODIS is an acronym for the Combined DNA Index System. This is a database containing forensic unknown, convicted offender and unidentified human remains/missing persons DNA profile information.
At the New Jersey State Police Office of Forensic Sciences the CODIS Unit can be broken down into two distinct sections. The first section is responsible for entering the data into CODIS, tracking the matches and notifying the appropriate law enforcement agencies regarding the hits. The second section is the CODIS laboratory, which is responsible for analyzing the DNA samples collected from convicted offenders who have qualifying criminal offenses in the State of New Jersey.
In New Jersey, CODIS has two levels. The state level, which is called SDIS for State DNA Index System and the national level, which is called NDIS for National DNA Index System.
The database contains various indices, however, the most commonly used indices are the offender index and the forensic unknown index.
The offender index contains DNA information on people convicted of an offense covered by the law in New Jersey at the time of their conviction. At the present time, a sample and information card are obtained from the convicted person and sent to the CODIS unit. The sample is given a bar code and the information card is retained in the CODIS unit. The only identifying information on the sample is this bar code. The sample is analyzed to generate a DNA profile at thirteen STR loci. After a quality control check, this DNA profile will be entered into the SDIS database. A complete profile (13 STR loci) can be uploaded to the NDIS database.
The forensic unknown index contains DNA profiles generated from crime scene stains. This data is then entered into the SDIS database. A complete profile (at least 10 STR loci) will be uploaded to the NDIS database.
Forensic unknown DNA profiles are searched against the offender index and the forensic unknown index weekly. Any matches (hits) are confirmed at the laboratory and the appropriate law enforcement agencies are notified of this investigative lead. At this time the agencies are instructed to obtain a reference sample from the offender for comparison purposes.
CODIS Frequently Asked Questions
Who came up with the idea for CODIS?
The DNA Identification Act of 1994 authorized the FBI to establish DNA indexes for: 1) persons convicted of crimes; 2) samples recovered from crime scenes; and 3) samples recovered from unidentified human remains.
When was it implemented?
In October 1998 the FBI introduced the National DNA Index System (NDIS) to exchange and compare DNA profiles electronically. This program is now widely recognized as CODIS (Combined DNA Index System).
Are all 50 states uploading information?
At this time, CODIS is installed in all 50 states and Puerto Rico.
How many samples has NJ uploaded?
There are over 95,000 samples in the NJ database; over 87,000 have been marked for upload to NDIS as of January 2007.
How has CODIS changed the way we solve crimes?
DNA is the tool that has changed how crimes are solved. CODIS is simply a mechanism to fully implement the DNA information.
What happens when a hit is developed in CODIS?
There are two types of hits, a forensic unknown to another forensic unknown (case to case) and a forensic unknown to a convicted offender (case to offender). When a forensic unknown matches a convicted offender sample, the matching convicted offender sample is re-run at the laboratory to confirm the match. Once the confirmation is completed a letter is sent to the investigator and respective Prosecutor’s Office informing them of an investigative lead. The investigator is instructed to collect a buccal swab control from the suspect to be compared directly to the forensic unknown.
When a forensic unknown matches another forensic unknown (case to case), the information is sent to both agencies, initiating a dialog and a sharing of facts from each case, which may eventually solve both crimes.
How many hits has NJ gotten thus far? Is this good or bad compared to other states?
There have been over 700 confirmed matches to the database as of January 2007. This is comparable to other states considering the size of the database.
What is an “investigative lead”?
Investigation aided is a term used when a criminal investigation has been assisted by the CODIS match.
Is there an international CODIS?
CODIS is installed in Belgium, Canada, Denmark, Estonia, Finland, France, Hong Kong, the Czech Republic, Italy, Netherlands, Norway, Portugal, Singapore, Spain, Sweden and the United Kingdom.
Why can’t you search suspects?
The law in New Jersey only allows convicted offender information to be added to the database, not suspects.
Are convicted offender samples collected right when a person enters prison?
Samples can be taken when a person enters prison, is transferred to another facility or leaves prison.
How is the CODIS program working in New Jersey?
The program’s success can be measured by the over 800 investigations aided since the inception of the program in the State of New Jersey. The database has solved homicides, sexual assaults, burglaries, kidnappings, aggravated assaults and a host of other crimes which may have gone unsolved were it not for the power of CODIS.
Can Mitochondrial DNA profiles be searched in CODIS?
Mitochondrial DNA profiles of convicted offenders and forensic unknowns (crime scene samples) are not searched in the Combined DNA Index System (CODIS) database. Since potentially many people can have the same mtDNA profile, such information would not be informative.
CODIS is used for searching mtDNA profiles of unidentified remains against those of missing persons and relatives of missing persons.
Currently the State of New Jersey collects approximately 28,000 convicted offender samples each year. The CODIS laboratory is tasked with analyzing these samples for upload into the State (SDIS) and National (NDIS) databases. The laboratory employs state of the art robotic technology to assist in the efficient and expeditious processing of the many hundreds of samples received each week into the CODIS unit.