Criminal Investigation and Evidence
Investigations succeed or fail on documentation. This domain tests warrant drafting, identification procedures, statement rules, and evidence handling.
Core rules
- Search warrants: G.L. c. 276, §§ 1 to 7. The affidavit must establish probable cause, a nexus between the place to be searched and the items sought, and particularity in describing those items. Stale information is a common defect.
- Chain of custody: label, seal, and log every transfer. A gap affects weight; a break can bar admission.
- Eyewitness identification: Massachusetts favors blind or double-blind administration, sequential presentation, unbiased instructions, and documentation, as discussed in Commonwealth v. Silva-Santiago (2009).
- Show-ups are permissible when prompt and justified by exigency, but suggestiveness is scrutinized.
- Custodial statements: unrecorded interrogation entitles the defendant to a cautionary jury instruction (Commonwealth v. DiGiambattista, 2004). Recording is the practical answer.
- Brady requires disclosure of exculpatory and impeachment material; officer credibility findings (Giglio) can end both a career and a prosecution.
- Drug and DNA analysis flows through the State Police crime laboratory; identity and weight are proven by certificate plus testimony.
Worked example
An officer develops a suspect in a package-theft series. Instead of a one-photo show-up, a sergeant builds a sequential, blind photo array with fillers matching the description, records the witness's confidence statement verbatim, and documents who administered the array. If the witness later identifies a different person, the file still shows a fair procedure, which is what survives a motion to suppress.
Traps
Writing that an informant is reliable without stating facts; using a single-photo show-up when no exigency exists; and destroying rough notes after the report is written.