Although there are numerous ways by which to categorize the forensic science disciplines, the committee found the categorization used by the National Institute of Justice to be useful:

1. general toxicology;

2. firearms/toolmarks;

3. questioned documents;

4. trace evidence;

5. controlled substances;

6. biological/serology screening (including DNA analysis);

7. fire debris/arson analysis;

8. impression evidence;

9. blood pattern analysis;

10. crime scene investigation;

11. medicolegal death investigation; and

12. digital evidence.⁵

Some of these disciplines are discussed in Chapter 5. Forensic pathology is considered a subspecialty of medicine and is considered separately in Chapter 9.

The term “forensic science” encompasses a broad range of disciplines, each with its own distinct practices. The forensic science disciplines exhibit wide variability with regard to techniques, methodologies, reliability, level of error, research, general acceptability, and published material (see Chapters 4 through 6). Some of the disciplines are laboratory based (e.g., nuclear and mitochondrial DNA analysis, toxicology, and drug analysis); others are based on expert interpretation of observed patterns (e.g., fingerprints, writing samples, toolmarks, bite marks). Some activities require the skills and analytical expertise of individuals trained as scientists (e.g., chemists or biologists); other activities are conducted by scientists as well as by individuals trained in law enforcement (e.g., crime scene investigators, blood spatter analysts, crime reconstruction specialists), medicine (e.g., forensic pathologists), or laboratory methods (e.g., technologists). Many of the processes used in the forensic science disciplines are largely empirical applications of science—that is, they are not based on a body of knowledge that recognizes the underlying limitations of the scientific principles and methodologies used for problem solving and discovery. It is therefore important to focus on ways to improve, systematize, and monitor the activities and practices