Criminalistics and Forensic Sciences
What this domain tests
Criminalistics and Forensic Sciences tests the scientific methods used to identify, preserve, and interpret physical evidence, and the legal rules that make that evidence admissible.
Core rules
- Criminalistics applies physical sciences to crime detection: dactyloscopy (fingerprints), ballistics, questioned documents, forensic chemistry, toxicology, serology, DNA analysis, and crime-scene photography.
- Forensic pathology determines cause and manner of death; forensic entomology uses insect evidence to estimate time since death.
- Chain of custody is the documented, unbroken record of custody, transfer, and analysis of evidence. Breaks can affect weight, and in drug cases may be fatal under RA 9165 as amended.
- The Rule on DNA Evidence allows DNA testing and provides for admissibility and post-conviction remedies. DNA results are not automatic proof; they are evidence to be weighed.
- Physical evidence must be relevant, authentic, and legally obtained. Illegal search or seizure can lead to exclusion under the Bill of Rights.
Worked example
In a buy-bust operation, officers seize sachets of suspected shabu. The marking must be done immediately at the scene, photographed, inventoried in the presence of the accused or representative, and witnessed by an elected public official and a media or DOJ representative. Each transfer is recorded. Reasoning: the chain of custody establishes that the substance tested is the same substance seized. If the marking or witnesses are missing without justifiable reason, the prosecution must explain the gap; otherwise the evidence may be excluded.
Traps
Do not confuse corpus delicti (the body of the crime) with the physical body. Do not assume a lab report proves identity without custody records. Do not treat DNA as conclusively identifying a person without proper collection and analysis. Watch for questions on probative value versus weight.