Recent improvements in DNA technologies have allowed for the successful collection and analysis of touch DNA from evidence where it was not previously possible.¹ These advancements have expanded opportunities to collect and identify forensic evidence that can potentially resolve violent crimes.

In collaboration with investigators, medical examiner and coroner (MEC) personnel can locate on a victim’s body where a suspect may have touched and deposited their DNA during a crime. Swabs of these areas taken at the scene or during autopsy may yield suspect DNA profiles sufficient for direct comparisons or upload into the Combined DNA Index System (CODIS).²

Once a victim’s body has been cleaned during autopsy and prepared for final disposition, opportunities to collect evidence that may link a perpetrator to the death have vanished. Considering the potential value of body swabs and touch DNA analysis in suspicious death and suspected homicide investigations, law enforcement and MECs should examine their policies and procedures related to evidence collection to ensure this potentially crucial evidence is not lost.

This article will present guidelines to help law enforcement and MECs ensure the preservation of critical evidence. The authors encourage agencies to standardize proactive collection of additional body swabs for touch DNA in all suspicious deaths and homicides. Following such practices can increase the chances of resolving violent crimes and, ultimately, serving justice.

Current Practice

Missed Opportunities

In most jurisdictions, a representative from the MEC's office will respond, along with law enforcement, to the scene of a suspicious death or suspected homicide to conduct an inspection of the decedent and begin collection of crucial evidence from the body. They focus specifically on samples that may be damaged or lost during transportation of the remains.

Presuming an autopsy is done, additional evidence may be collected because the forensic pathologist or other autopsy surgeon conducts a postmortem examination to help determine cause of death. Often, this is the final opportunity to collect evidence that could potentially link the perpetrator to the victim before the body is cleaned.

Literature has shown valuable DNA profiles can be obtained from an individual’s skin due to recent advances in touch DNA sampling techniques and methodologies. However, current recommendations and guidance on best practices for evidence collection do not reflect the importance of these developments.³

As of year-end 2018, only 17% of MECs were accredited by the National Association of Medical Examiners (NAME) and/or the International Association for Coroners and Medical Examiners (IACME), the main accrediting bodies for U.S. MEC offices.⁴ This implies that most MECs in the United States are not assessed for conformity to nationally approved standards regarding evidence collection, which could greatly impact law enforcement investigations.

Medicolegal death investigation (MDI) services and personnel training can vary widely between and within states and can result in disparities in evidence collection practices, to include those related to touch DNA samples.⁵ As such, critical touch DNA samples are not always collected, resulting in missed opportunities to potentially resolve violent crimes.

Case Studies

Two actual cases illustrate instances where touch DNA could have provided pivotal leads.

Example 1

An adult female was found stabbed, with mutilation wounds, in a public setting. Signs indicated that the perpetrator likely had significant contact with certain regions of the woman’s body, including her breasts and thighs. Both areas were void of blood at the scene and, as such, ideal for collection of potential touch DNA.

However, swabs of those areas were not taken at the scene. During the victim’s transport, blood from her wounds pooled and spread over her entire body. She was then washed in preparation for autopsy, eliminating the chances of collecting any touch DNA from the aforementioned areas.

Example 2

A teenage victim was suspected of being sexually assaulted before she was strangled and set on fire outdoors. It was apparent that she had been dragged by her feet/ankle areas. The majority of the girl’s body surface was significantly burned; however, her feet and ankles remained untouched by the fire.

No swabs of these areas were collected at the scene, and the victim’s body was washed for autopsy without the collection of valuable evidence at the morgue.

Research Methods

The authors employed a formative information-gathering design with two distinct phases to determine the extent to which touch DNA samples are collected through body swabs. First, they leveraged a preexisting dataset from the U.S. Department of Justice, Bureau of Justice Assistance’s Sexual Assault Kit Initiative (SAKI) grantees to capture initial information about touch DNA and its uses in casework.

Next, these data were compiled and anonymized and then shared with an 11-member expert panel consisting of seven medical examiners and four coroners. The goal was to determine whether any of these agency procedures should be considered promising or representing best practices and, thus, worthy of being shared more widely.

Finally, a literature review was conducted to see if these methods, procedures, or practices could be supported in peer-reviewed publications.

All information gathered from the SAKI sites, MEC personnel, and literature was examined to determine how agencies currently implement processes and protocols regarding the collection of additional body swabs for touch DNA analysis. Then, it was determined what recommendations can be made to help ensure valuable forensic evidence is not lost.

Discussion

DNA evidence can be a valuable part of any suspicious death or suspected homicide investigation and prosecution, potentially linking or excluding a suspect. More specifically, touch DNA can provide essential information about the physical contact (e.g., manual blunt force trauma, sexual assault, strangulation), or absence thereof, between a suspected perpetrator and a decedent.

Since DNA can be compromised during transportation of the body and again when the decedent is cleaned during the autopsy examination, there are limited opportunities to collect that evidence. It may be weeks, months, or even years before it is known whether the collected samples will be probative in nature. However, if DNA is not collected at the scene as needed or at the time of examination, that opportunity is lost.

Recommendations

Despite the potential importance of this evidence, few recommendations or published sources exist pertaining to the collection of additional body swabs in suspicious deaths or suspected homicides. Based on the existing SAKI dataset and in consultation with subject matter experts, the authors offer recommendations for consideration at the crime scene and/or during autopsy for these investigations to avoid the loss of potentially crucial evidence. These suggestions also apply to downstream DNA analysis as well as the implementation of standard operating procedures and policies regarding collection of the additional body swabs for touch DNA.

Additional body swabs should be considered in any homicide or suspicious death case involving likely or suspected physical contact.

Body swabs for touch DNA can prove useful in any homicide case involving likely or suspected physical contact. Sexually motivated homicides are most frequently thought of, but homicide investigations of strangulations and physical assaults of any sort, including child abuse cases, could also benefit from collecting such evidence. Even gunshot and stab wound cases may result from escalated violence between a perpetrator and decedent that began with physical contact and should be evaluated for body swab collection.

Often, it is unknown whether there was physical contact between the decedent and a suspect in deaths that are suspicious or of unknown circumstances — for example, cases involving a decedent found unclothed in a motel or with unexplained bruising around the neck, wrists, face, or arms. Also, it can be unclear what sort of contact occurred, such as in a possible child abuse-related case. These types of cases could also benefit from the collection of additional swabs in the event the ensuing investigation reveals foul play.

As this evidence can be lost during body transportation and MEC procedures, it is suggested to err on the side of caution and collect touch DNA swabs in any case that presents the possibility of significant contact with a perpetrator or that is suspicious in nature. Subject matter experts note the best practice is to always collect additional samples because homicides are often evolving investigations and information is typically still being gathered during the time of autopsy. Once the sample has been collected, it can then be decided later whether it should be submitted for analysis based on the findings of the continued investigation.

Body swabs should be considered both at the scene and during autopsy.

In consultation with the MEC, law enforcement should consider collecting body swabs at the scene of a suspicious death or suspected homicide if it can be done noninvasively by trained personnel. Factors such as weather (for an outdoor scene), extent of injuries that the forensic pathologist needs to examine, and/or transportation logistics should be considered in determining whether to collect evidence at the scene, to avoid potential loss, or during the autopsy.

Experts agree that the ideal place to collect these samples is within the controlled morgue environment during autopsy. However, swabs should also be collected at the crime scene prior to body transport when concerns arise about contamination or loss. For instance, a body will likely be at the scene for an extended time for crime scene processing, there may be adverse environmental or weather conditions, contamination of body surfaces by pooled blood could occur, and evidence could be lost during transport.

Areas of the body where additional swabs are collected should be based on scene findings and circumstances of the crime.

Determining what additional swabs to collect in a suspicious death or suspected homicide must be made on a case-by-case basis, with preliminary input from law enforcement and MEC personnel familiar with the scene findings and circumstances of the crime. By providing the forensic pathologist or medicolegal death investigator with this background information, law enforcement can inform recommendations for swabbing targeted areas of the body.

For example, if law enforcement indicates that it appears the assailant dragged the decedent by the legs during the offense, the forensic pathologist may choose to swab the victim’s ankles or other areas of the lower extremities. At a minimum, in suspicious death or suspected homicide cases, it is recommended that swabs be considered from exposed areas that can include the forehead, cheeks, chin, neck, breasts, nipples, arms, forearms, wrists, dorsal and palmar hands, knuckles, fingertips, thighs, legs, and feet.⁶

The consensus among MECs who confirmed having current practices in place regarding the routine collection of additional body swabs was that this extra step, including documentation, takes minimal time. Subject matter experts concur that, on average, it only takes 15 to 30 minutes to swab multiple bilateral areas of the body.

Based on the needs of the investigation, additional body swabs should be sent to the laboratory for DNA testing.

Most likely, these additional swabs will be tested at the request of the law enforcement investigator and/or attorneys assigned to the case. Law enforcement should carefully select the swabs for testing based on investigative needs, as opposed to routinely processing all swabs, to avoid overtaxing the crime laboratory.

Depending on the investigation, the request for analysis could be months or years after the swab(s) is collected, if at all. Therefore, the collection of these additional body swabs should not significantly impact the workload of crime laboratory personnel unless DNA testing is requested, as is typical with other potential evidence collected at the scene and at the time of autopsy.

Implementing standard operating procedures and policies can address logistical considerations associated with collecting additional body swabs.

To successfully implement these recommendations, law enforcement should work with the district attorney and MECs to develop policies and standard operating procedures to address some of the logistical questions they may encounter. This could include such topics as who will provide testing supplies; where, and by whom, will certain samples be collected (crime scene vs. autopsy); how chain of custody will be maintained; and where to store the samples until a determination is made regarding testing.

Case Studies

The following case studies are presented as supportive evidence for the recommendations highlighted.

Example 1

An adult female was strangled and beaten to death. Her body was found nude except for a single piece of clothing. Early investigation resulted in the arrest of the victim’s partner based on circumstantial evidence.

Body swabs, including those of the victim’s ankles, wrists, and arms, were taken at autopsy and yielded a consistent Y-STR profile that did not match the partner, resulting in his release from custody. A consistent Y-STR profile was also developed from the article of clothing. Further analysis of the clothing yielded an autosomal profile eligible to be entered into CODIS.⁷ Upon upload, authorities were notified of a match to an individual who was ultimately convicted of murder and received a life sentence.

Example 2

A young child was abducted on the way home from school. Her body was recovered several days later in the local landfill. It was evident that she had been sexually assaulted, strangled or suffocated, placed in a large plastic container, and then put in a dumpster as a means of disposal.

Despite exposure to heat, humidity, and environmental contaminants in the landfill, suspect DNA was successfully obtained from different areas of the child’s body. DNA that was eventually matched to her killer was obtained from swabbing of her genital areas and feet. When faced with the DNA results, the suspect provided a full confession to the crime and pleaded guilty.

Conclusion

In suspicious death or suspected homicide investigations, the collection of touch DNA evidence through body swabs at the death scene or during the autopsy provides a critical opportunity to link the suspect to the crime scene or victim. Collaboration among law enforcement and/or the investigator on the case and MEC personnel can help the MEC make informed decisions regarding where to collect swabs based on areas of the victim’s body the suspect may have touched and deposited their DNA.

DNA analysis of these samples should be based on the needs of the investigation. Further, MEC personnel have indicated the minimal effort needed to collect and retain these additional swabs should not overburden MEC offices, laboratories, or law enforcement agencies. Given the increasing sensitivity and capabilities of DNA testing, law enforcement and MECs should be mindful of the potential probative value of collecting body swabs. Failure to do so can result in a missed opportunity to collect critical evidence in the investigation.