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Low Copy Number Analysis From a Legal Perspective

Brad Leventhal
Queens County District Attorney's Office
Publication Date: 2010
Editor’s Note: At the 20th International Symposium on Human Identification, prominent figures in the DNA-typing field were asked to respond to a subset of specific questions posed during the low copy number (LCN) session. Brad Leventhal from the Queens County District Attorney's Office shares his responses below. Points of view expressed in this article are those of the author and are not necessarily shared by Promega.

Question: What do you see as the five biggest scientific issues/challenges/limitations with LCN testing in forensic cases, and how do you think they should be addressed by the scientific and legal communities?


1. What is the definition of LCN?

The definition of LCN is not an issue that can or should be answered by the attorneys. The definition of LCN is a scientific question that should be answered by the forensic laboratory that is conducting the procedure.

Of course, from a legal standpoint, it would be preferable for the forensic scientific community to generally agree as to what the definition of LCN is. However, the legal community should likewise understand that a particular scientific definition could vary from forensic lab to forensic lab based upon the equipment and procedures being utilized by the laboratory.

However, as a prosecutor, seeking to present LCN evidence in court it will be necessary to convince the court that whatever scientific definition is utilized by the forensic laboratory in defining LCN, the underlying science and the procedures employed are generally accepted within the relevant scientific community.

As a subset of this issue, the legal question that will need to be addressed is: Is this a novel scientific procedure, or is this simply a modification/enhancement of an already generally accepted scientific technique? The answer to that question, by a court, will determine whether a Frye or Daubert hearing will be required before such evidence is admissible in that particular jurisdiction.

2. Contamination

As we know, contamination can occur at various stages of a case involving forensic samples.
Contamination can occur in the lab.
Contamination can occur in the recovery and collection of the evidence at the crime scene.

Laboratories like the Office of the Chief Medical Examiner’s (OCME) in New York have taken tremendous precautions to minimize the possibility or likelihood of contamination in their lab, and they have detailed their procedures in their protocols.

However, it is equally important to minimize the possibility of contamination at the time of recovery by the law enforcement at the crime scene. Having the crime scene investigators gowned, gloved, masked and booted certainly is a precautionary step that will reduce the instances of contamination during collection. Additionally, as has recently been accomplished by the OCME, creating a database of DNA profiles of all crime scene investigators who are involved in the recovery and collection of the evidence is a big step toward addressing concerns of contamination by being able to identify the source of an unknown contributor that may be present in the sample.

3. Secondary Transference

I expect that because of the sensitivity of the LCN technique there will be much argument in the courtroom that the suspect’s profile, or perhaps the victim's profile, as the case may be, was detected not because the suspect or the victim touched the relevant item, but because someone else touched the relevant item and transferred the profile to the touched item.

This is an argument, as are most if not all, that can be made both in high copy number cases as well as low copy number cases. These are arguments that go to the weight that the fact finder wants to place on the evidence being received. While the heightened sensitivity of LCN makes this argument perhaps more prevalent, it is nothing new to forensic cases. It should be handled, as in all cases, by utilizing all of the other evidence in the case that will either support or not support the forensic results. While the issue of secondary transference is, of course, a scientific phenomenon, the application of the issue often plays itself out in the courtroom. In forensic cases, as in all criminal cases, each piece of evidence must be considered in light of all of the other evidence in the case. The issue of secondary transference is no different.

4. Qualitative vs. Quantitative Results

Certainly the ability of the forensic expert to offer a quantitative statistical probability on the DNA results is preferable in a court of law. However, in the absence of the ability to provide a statistical probability many jurisdictions have approved introducing a qualitative result, i.e., that the suspect cannot be excluded as a potential contributor to the forensic sample. The issue and the argument often made by adversaries to the introduction of this evidence is that it does not offer the fact finder any guidance as to what weight to give this evidence. However, that argument is specious because, as with many other types of scientific evidence, the pool of potential contributors can be voluminous. For example, take standard ABO blood typing, which might include half of the world population as potential contributors; this evidence has been received in court for decades and still is. Take, for example, hair typing where no DNA is available: the qualitative finding that the suspect's hair is consistent with the sample is permitted into evidence.

The qualitative result is providing relevant information to the fact finder. It is saying that the suspect cannot be excluded as a source of the sample. This by itself is insufficient to constitute proof beyond a reasonable doubt of the person's guilt but must be considered in light of all of the other evidence in the case.

5. Consumption of the Sample

Certainly one of the legal issues that we will see with LCN concerns the consumption of the sample.

The consumption of the sample will be likely to result in a variety of motions and legal maneuvers by defense attorneys who will claim that they are prejudiced by the consumption of the sample. The likely argument will be that because they can no longer conduct their own examination of the material they are thus prejudiced.

The two likely situations in which this will arise:
1. In the pre-arrest investigative stage where no arrest has yet to be made and the LCN testing is strictly in the early investigative stage.
2. In the post-arrest situation where a suspect has been arrested and the right to counsel has attached, and the LCN testing takes place thereafter.

In both situations the argument boils down to the potential inability of the defense to conduct their own independent scientific analysis of the relevant DNA material.

I believe that each forensic laboratory should have some protocols or procedures in place to deal with these types of requests by counsel.

This argument, as each of the others that I have addressed, bears on the weight and not the admissibility of the forensic evidence. A defense attorney is certainly able to make inquiry of the expert, in the presence of the fact finder, as to whether the sample was fully consumed and whether the defendant was thus able or unable to conduct their own tests. This once again, goes directly to the weight that the fact finder wishes to give the LCN evidence and not the admissibility of the evidence.

Question: What advice do you have to offer to forensic scientists working with attorneys on cases that may be considered "LCN" by some definition? What materials should be routinely provided in discovery when DNA testing is challenged?


The first piece of advice that I would offer is to encourage the attorney to come to the forensic laboratory and meet with the relevant personnel involved in the case.

There is a significant need for mutual education.

Chances are the attorney, as in my case, prosecutor, has had very little, if any, experience introducing DNA evidence at trial. Even if the attorney has had some experience dealing with standard DNA, the issues attendant with LCN are certainly different. Therefore, the attorney needs to be educated as to the nuances of LCN and the issues that accompany it, likewise, the forensic analyst, specifically in terms of the early stages of LCN usage in court, where a Frye or Daubert hearing is ordered. The forensic analyst probably has not been involved in a Frye- or Daubert-type hearing. The forensic analyst may or may not be familiar with the legal standards required to satisfy a Frye or Daubert test.

There needs to be a working relationship between the forensic lab and the attorney.

Another piece of advice to the forensic scientist when dealing with the attorney: they're attorneys, not scientists. They need to be educated as to the science and all of the concerns and issues that accompany LCN.

The forensic analyst and the attorney need to further understand that if a Frye hearing or Daubert hearing is ordered, such an endeavor is a huge undertaking and commitment. It requires many hours of preparation. It requires the attorney to have a better than mere-surface understanding of the science and how it needs to be applied in the law. And the forensic scientist and laboratory need to understand that, to undertake such a task, their laboratory will need to have put the time and money into their LCN program in regards to validation studies and the creation of appropriate protocols to mention just a couple.

As to the second part of this question, what discovery should be turned over depends in large part on the particular jurisdiction in which you may find yourself. Most jurisdictions have statute-based discovery rules that govern what and when certain materials are required to be disclosed to defense counsel.

In New York we are guided significantly by the discovery statute that is contained in our Criminal Procedure Law, specifically article 220 of that statute.

For the most part, when we are in the discovery stage of a proceeding it is at post-indictment, when we are dealing with felony crimes.

Usually we will turn over the entire case file that was generated by the state or city forensic laboratory. This will include all of the reports, case notes, vouchers, electropherograms, case contacts, police vouchers, requests for laboratory analysis by the relevant law enforcement agency, etc.

As far as providing laboratory validation studies, I would argue that, unless the prosecutor's office is involved in a Frye-type hearing, where validation studies could be relevant to the new or modified procedure, they are not proper discovery once Frye has been satisfied in the particular jurisdiction. For instance, I would highly doubt that in a standard DNA case the discovery of the laboratory's validation studies would be relevant. However, as to the laboratory's protocols, those could be discoverable, since it relates to whether the lab followed its own rules in conducting its examination of evidence.

How to Cite This Article

Scientific Style and Format, 7th edition, 2006

Leventhal, B. Low Copy Number Analysis From a Legal Perspective. [Internet] 2010. [cited: year, month, date]. Available from:

American Medical Association, Manual of Style, 10th edition, 2007

Leventhal, B. Low Copy Number Analysis From a Legal Perspective. Promega Corporation Web site. Updated 2010. Accessed Month Day, Year.

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