CODIS, NDIS, SDIS, Familial Searching (Partial Match and moderate stringency) and Arrestee and Offender Database Searches versus expungment

Are results expunged from the CODIS or SDIS databases and why should I care one way or another?

Maybe you are like me. I like it when crimes are solved. I like it when the true perpetrator is arrested, fairly tried and convicted. I like that there are prisons to house the truly dangerous.

But at what cost are we as a society and as a criminal justice system willing to pay to provide for this?

As a society we have been struggling with this for quite some time. One of the most valuable and powerful tools for crime solving are databases. Databases allow for computerized searching. Computerized searching means quick results. Quick results leads to quicker arrests. Quicker arrests may lead to prevention of crime for someone who is heck bent on being a serial criminal.

Admittedly, one of the very best computerized databases is the DNA Identification Systems both at the federal and state level. But at what cost are we expanding the population of these databases?

What one has to understand is the way that this data is used. Once a genetic profile is developed, it becomes part of the the SDIS (the State-based DNA Index System). For example, in my state, the Pennsylvania State Police maintains the Pennsylvania SDIS. Once in SDIS, that genetic profile is uploaded to the Combined DNA Index System (CODIS) provided that the state has a Memorandum of Understanding (MOU) (most states do) and if the profile generated if it meets the published quality criteria for acceptance.


Figure 1: An example of the route in FL to getting data into CODIS.

I am not convinced that in reality that records that should be deleted from the databases are actually being deleted. Here is why?

  1. How many criminal defense lawyers, when there is an acquittal, go through the process to obtain an expungment for state court records once charges has been dismissed or that there is an acquittal? Not all of us. Certainly not many Public Defenders or appointed counsel.
  2. How many times have criminal defense attorneys seen what we thought was an expunged record by way of signed court order still show up on either the NCIC (National Crime Information Computer) or the state police criminal history check? I sure have.
  3. How many criminal defense lawyers file and follow through to get a separate order seeking to remove from CODIS or SDIS data from overturned felony conviction, or if a sample is developed pursuant to a search warrant that the person is later found not guilty or have the charges dismissed? Almost none.
  4. Even if counsel remembered to do all of this at the state court level, no state court judge can force a CODIS expungment. Does the local SDIS repository notify CODIS as they are supposed to do per the MOU and per the DNA Identification Act of 1994 (42 U.S.C. §14132)? Do they honor it as a matter of comity? Beats me. You will never know. Why? CODIS is not subject to auditing.

So it seems to me that only in the most rare circumstance will a record ever be truly expunged from CODIS or a SDIS. It seems to me that unless it become part of regular activity by the defense bar, CODIS and SDIS will continue to grow and have records that it should not. Logically, the only way to prevent this non-designed expansion to happen is to get a state court order to order the state’s SDIS to expunge the profile, and then go into a Federal Court and get a federal court order to expunge the CODIS record.

My simple theory is this: once in there, it is in National DNA Index (NDIS) is like a diamond, it lasts forever. Even past death. There is no current mechanism of action to remove a genetic profile even after the physical capability of the person to commit crime is over because that person is dead.

Why is it that law enforcement wants to keep the genetic profile of someone even past death? (This is a question that I have been pondering and asking people for quite some time,)

For certain, a small part of that is to solve past crime. Say for example that a crime occurred some time ago. The cold case is re-opened, and it is discovered that for whatever reason, genetic evidence was present, but a profile was never developed.  In 2014, the genetic profile is developed and it goes into the forensic, unsolved crime database. In that case, searching the Offender Index or the Arrestee Index may provide useful. It comes up with a “match.” The case is closed. The victim or the victim’s surviving family is notified. And it also forecloses the possibility of a false arrest and a false conviction. This seems to be the prevailing argument for survival of DNA profiles in CODIS and SDIS after death. However, what no one will admit is that there is a far more useful reason why law enforcement wants to keep DNA profiles in SDIS and CODIS well past death…. familial searching. This, I suggest, is the real reason.

A familial DNA search is a search by law enforcement in DNA databases for genetic information indicating a relative of a person they seek to identify. Although it is recognized that parent-offspring will share one allele at every locus, full siblings may share two, one, or zero alleles at a locus. Siblings have a 25% chance of having no alleles in common, a 50% chance of having one allele in common, and a 25% chance of having two alleles in common. For more distant familial relationships, allele sharing decreases. The uncertainty in the probative value of the identification increases as we get more distant. First-order relatives will share more genetic data than unrelated individuals. There are certain metrics such as relationship index (kinship index) that can be used to arrive at a likelihood ratio (called the combined relationship index) of the likelihood or relation that have been used for years in court to establish paternity or lineage in estate cases for probate purposes. Certainly these CRI and LR ratios are not without flaw as unrelated folks may have higher LRs due to random chance allele sharing, but it is still a tool that is used in civil and family court. However, if you ever want to see a swift and angry response from a state DNA analyst simply mention the phase “familial search.”

On a daily basis, thousands of computerized searches are completed without a warrant and without probable cause to try to “match” the Convicted Offender and/or Arrestee Database and/or Legal Indices of the various SDIS databases and the CODIS to the Forensic (casework or unsolved crime) database.

Although the FBI claims that they do not do “familial searching” (brother’s keeper searching or family DNA searching), they absolutely do. According to this link ( they admit that they conduct CODIS searches at

moderate stringency.  Moderate stringency is defined as a search that requires all alleles to match, but the target and candidate profiles can contain a different number of alleles.

For those who know DNA and CODIS searching that is by definition a familial search. They even admit to “partial match” reporting which is also code for familial searching. Although later on they try in the same document to refine what they believe is familial searching per SWGDAM, which they say is the purposeful searching of family members as opposed to an un-targeted general search of everyone that just so happens to end up with closely related people (i.e., family), the end result is the exact same. Same pants different pocket. In many states, the same is true. They report partial matches or do moderate stringency searches which result in a list of the most closely associated hits.

Now that is scary stuff to me and should be to you.


Because with the “partial match” result or the “moderate stringency” result, it becomes the horrible “round up the usual suspects” dragnet that sweeps up the innocent with the not so innocent like the dolphin in the old fashioned tuna nets.

All the way back in 1969, our SCOTUS found such a method to be totally unacceptable in the case of Davis v. Mississippi U.S. 721, 727 (1969). In Davis, a rape victim described her assailant as an African American youth. Police rounded up dozens of local youth who met that profile, processed them, and took fingerprints until a match with a print on the victim’s window was found. In that case nearly 50 years ago, the United States Supreme Court found that the Fourth Amendment protected against fingerprinting without individualized suspicion. The government can never conduct blanket searches just for the sole purpose of solving crimes – yet it does this with CODIS every single day, and familial searches by whatever name “moderate stringency” or “partial matches” does exactly this.

But this problem will compound when all states go to an Arestee DNA collection scheme. In this post Maryland v. King world, thirty-two states have legalized collecting DNA from people arrested for crimes before they’re convicted.

The defense community needs to be diligent in getting people out of SDIS and CODIS for the sake of justice and the innocent.

[Off soapbox]

4 Responses to “CODIS, NDIS, SDIS, Familial Searching (Partial Match and moderate stringency) and Arrestee and Offender Database Searches versus expungment”

  • A point of clarification.

    The moderate stringency seaching in CODIS as referred to in the FBI quote is not the equivalent of familial searching.

    Moderate stringency searching as standardly applied in CODIS stems from the operational reality that different labs use different commercial kits, and the kits will differ in two important respects:

    1) they will differ in the selection of loci that are tested. While all kits have the core CODIS loci, they may have additional loci which are not shared between kits. So the profiles that are developed will consist of different sets of loci.

    2) Kits may test for the same locus, but they may use different applification primer sets to do the testing. Mutations in primer sets that prevent amplificaton are present in the population at low frequency. But they are specific to the primer site. So a primer site mutation that affects one kit, may not affect another kit. So a 2 peak heterozygote in one kit may appear as a 1 peak homozygote (sort of, not taking into account peak height considerations) in a different kit.

    For these reasons, high stringency searching that looks for exact matches across a defined set of loci would miss many hits of interest.

    Familiar searching is a much different thing,

  • Thank you Professor Tim Sliter,
    While I understand and appreciate your comments in that I have posted them. I understand your points. However, how is the end result any different? I am not talking about the process. I am talking about the result.

  • There is a very distinct difference in the end results of non-familial and familial database searches. The differences are best illustrated by an example.

    Suppose a young woman is beaten to death. Her fingernails are broken and torn, suggesting that she fought with her assailant. DNA of fingernail scrapings gives a mixture of her DNA and the DNA of a male. The lab generates a profile for the male component that can be submitted to CODIS. However, because the sample is a mixture there is some ambiguity at certain loci. For instance, the male might be homozygous at a particular locus, or he might be heterozygous and share an allele with the victim.

    If the assailant is a convicted offender whose profile is in the CODIS database, then most people would want the police to identify this person through a database search. However, because of the ambiguity issue, it is likely that a high stringency search would be unsuccessful at identifying the matching convicted offender record, whereas a moderate stringency search would likely be successful. This is what the standard FBI search – which is non-familial – would give: a candidate for the source of the evidence profile.

    The FBI search would not return any record corresponding to the brother or the father of the assailant. But a familial search would give exactly that. Familial searches return candidate relatives of the person who left an evidentiary DNA profile. If the assailant’s father is a convicted offender, then a familial search could (in theory) identify that convicted offender as being a possible biological relative of the male who contributed to the fingernail DNA. The familial search might return more than one candidate relative. Some of those candidates might be spurious, which is why followup investigation is needed. But that is true for all CODIS database hits.

    Again, my point is not to say that familial searching is good or bad, desireable or undesireable, correct public policy or incorrect public policy. My point is just that it is different from standard moderate stringency database searching.

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