Forensic Analysis Part 1

Forensic Chemistry: The study of chemical substances in relation to criminal investigations, focusing on the identification and analysis of materials such as drugs, toxins, and explosives.

Sections of Forensic Chemistry analysis:

  • Controlled Substances

  • Toxicology

  • Explosives

  • Trace Evidence

  • Latent Prints

  • Firearms

  • Tool marks and impressions

  • Questioned documents

Criminalistics: the branch of forensic science focused on evaluating physical evidence collected at crime scenes.

Forensic Labs to do more than just crime scene analysis. They also analyze environmental samples.

Primary vs. Secondary Providers

  • Primary: Federal, state, and local law enforcement agencies. They are accredited organizations that have rigid procedures that allow for their findings to be considered to be reliable.

  • Secondary: Private and university laboratories. These are very common in Europe and other parts of the world. Secondary providers may have different accreditation standards and procedures, which can affect the reliability of their findings.

What is physical evidence?

Physical evidence refers to any tangible object that can be collected and analyzed during an investigation, such as fingerprints, hair, clothing fibers, weapons, or any material that can help establish a link between a suspect and a crime. Additionally, it includes items like soils, glass fragments, and bullets, all of which can provide critical insights into the circumstances surrounding the crime.

It is crucial that this evidence is properly collected, preserved, and documented to maintain its integrity and ensure accurate analysis. This is very important because the collection of physical evidence is subject to search and seizure laws. If the evidence is concrete, but not collected properly, it is still inadmissible in criminal proceedings.

How do you keep evidence “pure” at a crime scene?

CARE MUST BE TAKEN

You have to be very careful not to introduce outside contaminants such as:

  • DNA, fingerprints, hairs, and clothing fibers that may compromise the integrity of the sample.

  • The evidence is packaged based on the type and physical characteristics.

  • In order to ensure evidence is not altered or damaged, each item must be packaged separately.

Physical vs. Other Types of Evidence

  • Direct vs Circumstantial Evidence

  • Physical Evidence has class and individual characteristics

What are class characteristics?

  • Characteristics shared by all members of a particular class. While they cannot be attributed to a single source, the can be used to conclusively eliminate association with a suspect or source location.

  • Think of mass produced products. They often only have class characteristics unless a change to the item has been damaged in some way. Such as:

    • a tear, breakage, or wear pattern that would give the item individual characteristics.

How can class characteristics turn into individual characteristics?

  • Brand of shoe on the sole→ Wear pattern on the sole

  • Diameter of firearm barrel→ striations on bullet

  • Density of broken glass→ Fit of broken pieces to make the whole panel

  • Drug identity→ trace metals that attribute to the lab that it was created

  • Species origin of hair→ DNA ID from follicular tag

  • Make, model, and color of vehicle→ serial number of vehicle

  • A typed letter→ Angle and wear on a type writer

Life ensures wear and tear of different physical evidence. The overall purpose is to narrow down the source, so that you can individualize it to the point of no contention.

What are individual characteristics?

  • These are unique characteristics that can be used to associate an object to a particular individual, suspect or place associated with a crime.

More Examples of Evidence Types:

  • Methamphetamine:

    • On first glance, it is a white powder

    • In order to gain more information, you would perform a presumptive test such as a Marquis test, a positive reading would allow for further analysis of the materials.

    • Now that we have proof of the substance, we need to locate the origin of the product.

      • This is done through processes such as Mass Spectrometry. This will allow for analysis of the trace chemicals that are used in production. Since these illegal meth labs are not following proper PPE, and don’t have standard tools in order to purify their product,

        • These materials are synthesized using chemical techniques such as:

          • instrumentation and statistical methods.

  • Firearms:

    • The class characteristics may include:

      • The type of gun, (a revolver of .38 caliber), the number of lands, grooves, and hand twist impressed on bullets fired with weapons.

    • The Individual characteristics may include:

      • Striated markings that can be observed on the bullets shot by a particular revolver which result from the unique imperfections and wear patterns of that specific firearm.

Evidence Classification/Categorization:

  • After evidence is identified, the first step might be to perform an in field presumptive test in order to tentatively determine the identity of the substance or to determine the class of materials to which it belongs.

  • If the substance remains of value to the case, the item is packaged and labeled.

  • At the lab, criminalists will perform further presumptive or screening tests.

  • Based on the results, different analytical techniques may be employed to confirm the presence of specific substances, such as gas chromatography or mass spectrometry.

  • Additional analysis will be performed to determine the quantity of the components in the sample.

How can a criminalist determine if two objects originated from the same source?

  • They first need to compare the item in question (Q) to the item of known (K) origin.

    • One example is comparing an piece of broken plastic from a headlight cover to the still intact portion.

  • Comparisons are done using microscopy, which allows for the examination of surface features and structural characteristics that can reveal similarities or differences between the two pieces.

  • Reference samples are collected from a different area than the evidence but have a known or authenticated source or composition. These may include hairs from victims/suspects, buccal swabs, unburned or unstained areas of fibers or fabrics, or unaltered paint from a car involved in a “hit-and-run”.

Forensic Analysis from the Scene to the Crime Lab

  • Sometimes reference samples are not available. In order to determine the source of the evidence, criminalists rely on databases assembled for this purpose. This could be the IAFIS database for fingerprinting.

  • Comparison standards may also be used to determine the identity of materials.

    • These standards have a known identity and have a trusted source or origin.

      • NIST produces various standard reference materials for purchase and come with certification paperwork.

      • ASTM also provides reliable source material.

  • It is crucial to use care when working with standards. Like anything, these can become contaminated. Proper handling and storage techniques must be employed to maintain their integrity and to ensure the safety of the criminalist.

What are Evidence Standards?

  • These are standards provided by the NFPA. This diamond is often included in the SHS and includes information colored and numerical code for health, fire, reactivity, and special hazards.

What are the categories of the NFPA diamond?

  • Health: Indicates the level of health risk posed by the material, rated from 0 (no risk) to 4 (extreme risk).

  • Fire: Indicates the material's flammability, also rated from 0 (will not burn) to 4 (highly flammable).

  • Reactivity: Shows the stability of the material and its potential for chemical reactions, rated from 0 (stable) to 4 (may detonate).

  • Special Hazards: Denotes specific hazards that may not be covered by the other categories, often represented by symbols such as "OX" for oxidizers or "ACID" for acid hazards.

Standards and Controls

  • This is the used of controls, standards and blanks.

  • They are used to reveal potential problems with the test or procedure.

  • Background controls are run to test that the background interference is minimal and does not affect the overall results of the analysis.

  • A negative control is also included in a well designed experiment and should not produce any response or a known negative response for the test.

Testing

  • It is important that your results can be done multiple times to ensure the accuracy and precision of your results.

    • High accuracy and high precision are characterized by hitting a bullseye repetitively in the same spot with each trial, indicating that the measurement process is reliable and valid.

    • High precision but low accuracy is characterized by hitting the same spot consistently, but not near the true value, reflecting a systematic error in the measurement technique.

    • Low precision but high accuracy is characterized by hitting the true value sporadically while the measurements vary widely, indicating inconsistency in the methodology used.

Why are Standard operating procedures (SOPs) important?

  • Standard operating procedures (SOPs) are important because they provide a clear framework for conducting forensic analyses, ensuring consistency and reliability across different cases. They help minimize variability in procedures, reduce the risk of errors, and enhance the overall integrity of the evidence collected.

Where do SOPs come from?

  • SOPs are typically developed by institutions or organizations based on regulatory guidelines, industry best practices, and input from experienced forensic scientists and analysts. They have been published and accredited.

  • Additionally, many SOPs undergo regular reviews and updates to incorporate new technologies and techniques, ensuring that forensic practices remain current and effective.

What is Quality Assurance in Forensics?

  • Quality Assurance in Forensics refers to the systematic processes and procedures implemented to ensure the reliability, accuracy, and validity of forensic analyses. This includes regular calibration of equipment, training of personnel, and adherence to established protocols to mitigate errors and maintain the integrity of the forensic evidence.

How can a criminalist convince the jury of the accuracy of their findings?

  • This can be achieved by clearly presenting the methodology used during the analysis, demonstrating adherence to quality assurance standards, and providing evidence of proper training and experience, which collectively reinforce the credibility of their results.

  • It is also crucial for the criminalist to have the right credentials and to establish their expertise through relevant certifications and a history of participation in professional development activities.

  • Additionally, they have to present it in a way that someone without a background in the field will understand.

  • This involves using visual aids, simplifying complex terminology, and engaging in straightforward explanations that connect the scientific findings to the case at hand.

  • The last barrier is to receive the judge’s approval before any forensic evidence can be introduced in court, ensuring that the methods used are deemed scientifically valid and reliable.

When will a judge accept an expert witness?

  • First the methodology has to be sound, peer reviewed, accurate and precise. When accepting new methodology, the judge will take into account that precision is not there. However, once it is accepted, a precedent has been set.

  • Continued advancements will allow for peer-reviewed literature and science-backed criminal hearings.

Industry Defined Standards: The legal system relies on established criteria to determine the qualifications and reliability of experts, ensuring that their testimony adheres to recognized scientific and technical standards.

SWGDRUG Categories A-B-C:

  • Category A

    • Provides molecular structure information

    • Theoretical relation between the molecular structure of the analyte and the observed data

    • Predictability- Expert analyst can predict/explain spectral changes

  • Category B

    • Does not provide molecular structure information

    • Limited predictability

  • Category C

    • Significant interferences

SWGDRUG RECCOMENDATIONS:
Category A: IR, MS, NMR, Raman, X-ray diffractometry

Category B: CE, GC, IMS, LC, Microcrystalline Tests, Pharmaceutical ID, TLC

    Category B (cannabis only): Macro-Examination, Micro-Examination

Category C: Color tests, fluorescence, Immunoassay, Melting Point, UV

Why is research important?

  • Research allows for criminalists to identify and seek to understand materials that are not controlled to help the legal system enact new laws in order to keep society safe. If you don’t know what the substance is, how do you know to make it illegal?

How do criminalists yield sufficient chemical information to solve chemical structures?

  • This is done by coupling methods such as NMR spec, Mass spec, melting point, and IR spec.

What does ab initio mean?

  • Ab initio refers to a method of calculation in quantum chemistry where properties are deduced from first principles without empirical parameters, allowing for a precise approach to understanding molecular structures and behaviors.