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The expert should ensure that the attorney understands the distinction between objective (supported by science) and subjective (opinion) statements and uses them appropriately.
The attorney should also be made aware of the expert's assumptions and the presumptions he uses in formulating opinions, as opposed to facts supporting conclusions, or a combination of both (e.g., using presumptive tests to identify biological fluids).
An expert may testify like any other witness about facts about which the expert has personal knowledge, even if the expert was able to observe and assess the relevancy of those facts only because of special skill or experience.
An expert may also offer opinions related to facts about which the jury itself has insufficient experience to form an intelligent conclusion. The expert does not need to be certain of which facts the opinion is based on as a condition of its admissibility. It is sufficient that the testimony of a particular result is within the range of reasonable probability according to generally accepted scientific principles.
An expert should explain the limitations of results (e.g., two hairs being microscopically consistent does not mean that they originated from the same source).
Additional Online Courses
- What Every First Responding Officer Should Know About DNA Evidence
- Collecting DNA Evidence at Property Crime Scenes
- DNA – A Prosecutor’s Practice Notebook
- Crime Scene and DNA Basics
- Laboratory Safety Programs
- DNA Amplification
- Population Genetics and Statistics
- Non-STR DNA Markers: SNPs, Y-STRs, LCN and mtDNA
- Firearms Examiner Training
- Forensic DNA Education for Law Enforcement Decisionmakers
- What Every Investigator and Evidence Technician Should Know About DNA Evidence
- Principles of Forensic DNA for Officers of the Court
- Law 101: Legal Guide for the Forensic Expert
- Laboratory Orientation and Testing of Body Fluids and Tissues
- DNA Extraction and Quantitation
- STR Data Analysis and Interpretation
- Communication Skills, Report Writing, and Courtroom Testimony
- Español for Law Enforcement
- Amplified DNA Product Separation for Forensic Analysts