Zimmerman: Importance of the Chain of Custody

One of the most overlooked, but nevertheless important, issues in any trial is whether the evidence presented by the prosecution to support its case is in the same condition as it was when the police seized it. The integrity of the evidence has been important to creating and sustaining legitimacy and confidence in the ability of a formal dispute resolution process ever since people began to settle in permanent communities along river banks and support themselves year-round by fishing the rivers and growing crops in the fertile soil along the river banks.

We are more aware today of the necessity to protect the integrity of the evidence because of the unique sensitivity and ability of DNA testing to identify the specific human source of trace amounts of blood evidence invisible to the human eye. Jurors and defendants have a right to expect that police and prosecutors will protect the integrity of the evidence at all times when it is within their possession, custody or control. Defense counsel have a duty to their clients to examine the evidence before trial and review all of the documentation regarding who handled it and where it has been since it was seized.

A reasonable doubt that a defendant committed the crime charged can arise from the evidence or lack of evidence. If the evidence in a case appears to have been tampered with or its papers are not in order, I would expect the defense attorney to argue that an acquittal is appropriate.

Chain of custody is the legal term that lawyers and judges use to describe the record-keeping trail from the crime scene and the Medical Examiner’s Office, where most evidence exhibits are collected, to the property room at the law enforcement agency’s offices to the Crime Lab, for testing and analysis, and back to the property room where it will be stored until needed for trial.

Every police department property room should be a secure facility accessible only by authorized personnel. Evidence log books are maintained in the property room, typically at the front desk. The logs record from whom evidence was received and when it was received as well as to whom it was released, when it was released, and why it was released.

Access to evidence stored in the property room is restricted to people with security clearances who work there. Only authorized officials, such as police officers and prosecutors are permitted to examine evidence. They are not permitted to enter the property room to retrieve it. Instead, they have to go to the front desk and request the item or items they want to see. The items are placed in a conference room for them to examine and replaced in storage after they are done. Appropriate entries in the log book are recorded to identify who examined what items of evidence and when they examined them.

The process of evidence collection in the Zimmerman case began shortly after 7:30 pm on February 26th in the Retreat View neighborhood and continued the next day at the Medical Examiner’s Office at the autopsy. Most of the items collected would have been placed in brown paper bags, which are the preferred method of storage because they allow sufficient air to circulate and keep the exhibit dry. The bag would have been sealed with tape, and marked with a preassigned exhibit number preceded by the first and last name initials of the person who collected exhibit. Exhibits collected at the Medical Examiner’s Office will be preceded by the initials ME. For example, Exhibit ME-12 is the number assigned to Trayvon Martin’s hooded sweatshirt.

After securing the bags so that they cannot be opened without leaving an easy to detect cut, the forensic officer would have placed his signature on the bag at a location where the writing spans an area of the bag partially overlapping the surface of the bag and the tape to secure it. This would prevent someone from escaping detection by removing the tape to get into the bag and replacing the tape.

Police property rooms also have rooms devoted to drying out evidence before it is stored. Bloody clothing, for example, must be dried out before it is stored or the blood will decompose and the DNA will break down potentially preventing a successful DNA analysis. Dried blood stains are the best way to preserve blood for subsequent DNA analysis since they will last indefinitely. Blood samples and other biological evidence are stored in refrigerators.

When defense counsel decide to look at one or more of the items in evidence in a case, the standard procedure is to call the prosecutor assigned to handle the case and schedule a mutually convenient time to meet at the front counter outside the Property Room.

The meeting would take place in a reserved conference room with all of the bags containing evidence in the case already present.The table would be covered with butcher paper to catch any trace evidence that might be dislodged when items are examined. Working off an inventory list, defense counsel would request by number the items that it wants to examine.

After everyone puts on vinyl gloves to avoid contaminating the evidence while handling it, a forensic or evidence collection officer from the investigative agency would cut an opening large enough to reach in and renove the object in order to examine and photograph the particular item of interest. Magnifying glasses and portable microscopes are used to detect and examine trace evidence, such as blood and fibers.

The forensic official would then replace the item inside the bag and reseal it with tape signing the bag so that a portion of the signature is present on the tape as well as the bag.

If I were representing George Zimmerman, I would have requested copies of the log books so that I could track the location of each item of evidence at any point in time since it was seized. I would want to know, for example, what items were sent to what section of the crime lab for testing. I would compare the forensic reports that have been released with the information in the log books to determine if anything is missing. I would specifically request any reports that appear to be missing.

If I were to find a gap or incomplete or confusing entries in the log books regarding any item of evidence, I would prepare a motion to exclude that item from being mentioned or admitted at trial into evidence on the ground that, given the information in the log books, the prosecution cannot lay a proper foundation.

In other words, the prosecution should not be permitted to mention any item of evidence or present any testimony about any test results obtained for that item, unless it can show an unbroken chain of custody that would assure the integrity of the item for the jury.

The general rule today is that trial courts have discretion to grant or deny these motions and may require actual evidence of tampering that casts doubt on the validity of the results. Every good lawyer always makes an objection on the record, however, to preserve the issue for appeal.

Even if the motion to exclude is denied, defense counsel should always argue that the break in the chain of custody supports a reasonable doubt.

I also would specifically request the laboratory bench notes prepared by each forensic scientist for each analysis that he or she performed. Laboratory bench notes are handwritten notes generated at the bench by each scientist to record what they did and when they did it with each item of evidence that they examined. They also indicate when they obtained each item from storage at the crime lab and when they returned it.

Forensic scientists generate their reports from the information recorded in their bench notes. The only way to determine what tests they performed and whether they followed the proper protocol or procedure for each test is to look at the bench notes.

I also would request the vitae and results of proficiency tests taken by each forensic scientist.

Meanwhile, I would already have begun to assemble a team of forensic scientists who specialize in various areas relevant to this case. After I had assembled the team, I would schedule a meeting for all of us to get together to discuss the case and create punch lists of tasks that need to be done.

At some point in the relatively near future, I would want to view the evidence and I probably would want some of my experts to be there as well, particularly my blood stain and trace evidence analysis experts.

Finally, forensic fraud, which has been identified as one of the seven causes of wrongful convictions of innocent people, is a major problem in this country. Criminal defense attorneys, who truly are liberty’s last champion because they fight to protect the constitutional rights of all citizens when they fight to protect the constitutional rights of their clients, need to get over their fear science and be ever vigilant and aggressive in scrutinizing the work of forensic scientists.

They represent our best chance to clean-up forensic science.