What are two methods of identification for skeletal remains?

According to the National Institute of Justice, DNA analysis is considered the gold standard for identifying human remains. Forensic science offers several reliable methods, but the two primary and most conclusive methods for answering the question, "What are two methods of identification for skeletal remains?", are DNA analysis and forensic odontology, or dental record comparison.

Quick Summary

This article explores the highly accurate and scientific methods of DNA analysis and forensic odontology for identifying human skeletal remains. Both techniques rely on unique, individual characteristics—genetic markers and dental features—to provide positive identification, often in cases where the body is unrecognizable.

Key Points

• DNA Analysis: The most conclusive method for identification, often requiring a comparison of a profile extracted from bone or teeth with a reference sample from a victim or their relatives.

• Forensic Odontology: Compares unique dental features, such as fillings, crowns, and X-rays, from the remains with antemortem dental records to establish a positive match.

• Superiority and Limitations: DNA is more definitive but can be degraded, while dental records are highly reliable but depend on the availability of existing patient records.

• Complementary Techniques: Forensic anthropologists use other methods like estimating a biological profile from skeletal traits and tracing surgical implants to aid the identification process.

• Disaster Identification: In mass fatality events, both DNA and dental analysis are critical for identifying victims, particularly when bodies are severely compromised by fire or trauma.

• Advanced Methods: Techniques like forensic genetic genealogy and comparative radiography offer further avenues for identification, especially in cold cases.

• Combined Approach: The most effective strategy combines multiple identification methods to increase the certainty and speed of identifying human remains.

Forensic DNA Analysis for Identification

DNA analysis, or forensic DNA typing, is often the most conclusive method for identifying human remains, especially when remains are severely degraded, burned, or fragmented. The process involves extracting genetic material from tissues that are resistant to decay, like bone and teeth, to create a unique DNA profile. This profile is then compared against a known reference sample to establish identity.

The Process of DNA Extraction and Comparison

1. Sample Collection: Forensic teams collect samples from skeletal remains, often prioritizing dense bone from the femur or teeth, as these tissues offer better preservation of DNA. A control sample is also taken to rule out contamination.
2. Laboratory Extraction: In the lab, DNA is isolated from the bone or tooth material. For ancient or highly degraded remains, techniques to extract mitochondrial DNA (mtDNA) are sometimes used, which can confirm maternal lineage.
3. DNA Profiling: The extracted DNA is amplified using techniques like Short Tandem Repeat (STR) analysis, which examines specific repeating DNA sequences. A profile based on these repeats is generated.
4. Database Comparison: The generated DNA profile is compared to samples in national databases like the Combined DNA Index System (CODIS) or state missing person databases. Matches can be made directly with an individual's previously collected sample (e.g., from a personal item) or indirectly through familial matching with a close relative.

The Rise of Genetic Genealogy

In recent years, forensic genetic genealogy has become a powerful tool, particularly for cold cases. This involves uploading a DNA profile to public genealogy databases to find distant relatives of the deceased. With the assistance of a forensic genealogist, a family tree can be constructed to narrow down potential identities, providing law enforcement with new investigative leads.

Forensic Odontology (Dental Records) Comparison

For decades, forensic odontology, the application of dental science to legal matters, has been a cornerstone of victim identification. Teeth are remarkably durable, often surviving conditions that destroy other soft and hard tissues, making them a reliable source for identification after disasters or extended postmortem intervals.

The Comparison of Dental Features

• Unique Characteristics: A forensic odontologist compares dental features observed in the remains with antemortem (pre-death) dental records of a missing person. These include the unique placement of fillings, bridges, crowns, and root canals, as well as the natural spacing, shape, and alignment of the teeth.
• Radiographic Evidence: X-rays are a critical component of this comparison. By aligning antemortem X-rays with postmortem images of the recovered dental arcade, experts can look for matching structural details that confirm a positive identification.
• Tracing Implants: In some cases, dental implants, dentures, or other appliances may have serial numbers that can be traced back to the manufacturer and patient.

Comparison of Identification Methods

Feature	DNA Analysis	Forensic Odontology (Dental Records)
Accuracy	Extremely high; considered the gold standard.	Very high, especially with comprehensive dental work.
Reliability on Remains	Can be successful with highly degraded or fragmented bone and teeth.	Very reliable, as teeth are extremely durable and resistant to decay and fire.
Information Required	A known DNA sample from the victim or a close relative.	Antemortem dental records (X-rays, charts) of the presumed victim.
Best for Mass Disasters	Excellent, especially when fragmentation and degradation are widespread.	Excellent for disaster victim identification (DVI) where many records are available.
Time and Cost	Can be time-consuming and expensive, especially with complex familial searches.	Generally faster and less expensive than DNA analysis, assuming antemortem records exist.
Limitations	May be impossible to obtain a usable profile if DNA is too degraded or contaminated.	Depends entirely on the existence and quality of antemortem dental records.

Other Supportive Methods

While DNA and dental records are primary identifiers, forensic anthropologists use other techniques to create a biological profile that can aid in the search for a match:

• Skeletal Analysis: Examining skeletal features allows anthropologists to estimate age, sex, ancestry, and stature of the individual, which significantly narrows the search for missing persons.
• Surgical Implants: Tracing the serial numbers of surgically implanted devices, such as pacemakers or orthopedic screws, can help identify a person through hospital records.
• Comparative Radiography: This technique involves comparing postmortem X-rays of skeletal features, such as healed fractures or unique sinus patterns, with antemortem images for a definitive match.
• Facial Reconstruction: While not a definitive identification method, creating a physical or digital facial approximation from the skull can generate new public leads when other identifiers are unavailable.

Conclusion

When faced with unidentified skeletal remains, forensic investigators rely on a combination of techniques, with DNA analysis and forensic odontology being two of the most powerful and conclusive. DNA provides a definitive genetic match, even from ancient or highly degraded material, while dental records offer a robust comparative method based on the highly durable nature of teeth. These two scientific approaches provide the most reliable pathways to identifying the deceased and bringing closure to families. Other supportive methods, from skeletal analysis to surgical implant tracing, supplement these primary techniques, creating a comprehensive strategy for solving unidentified persons cases.

Frequently Asked Questions

What is the most reliable method for identifying skeletal remains?

While multiple methods can be used, DNA analysis is generally considered the most reliable and is often referred to as the 'gold standard' in forensic science. Forensic odontology is also highly reliable, particularly in cases involving fire or advanced decomposition.

Can DNA be extracted from very old skeletal remains?

Yes, DNA can be extracted from ancient remains, even those over 200,000 years old. Teeth and dense parts of bone, like the femur, are typically the best sources for recovering viable DNA.

How do dental records help identify remains?

A forensic odontologist compares dental X-rays and charts of the deceased with antemortem records from a missing person. Unique features like fillings, crowns, and tooth alignment allow for a conclusive match.

What is the role of a forensic anthropologist?

A forensic anthropologist examines skeletal remains to determine a biological profile, including the individual's estimated age, sex, ancestry, and stature. This information helps narrow the search for a missing person to find a potential match for dental or DNA records.

What if dental records are unavailable?

If dental records are unavailable or insufficient, investigators can rely on other methods, including DNA analysis, tracing surgical implants, comparative radiography, or creating a facial reconstruction to generate leads.

What is the difference between nuclear DNA and mitochondrial DNA (mtDNA)?

Nuclear DNA provides a unique profile for an individual. Mitochondrial DNA, inherited from the mother, is less unique but is often more stable and can be used to confirm maternal lineage, especially with older or degraded remains.

How accurate is facial reconstruction?

Facial reconstruction, or facial approximation, is an investigative tool used for recognition, not positive identification. It provides a likeness of the person's face based on the skull and is used to generate public leads, which can then be followed up with definitive methods like DNA or dental analysis.