Investigations and Evidence Handling
This domain tests whether your investigations can survive suppression and whether your evidence handling can survive a chain-of-custody challenge years later.
Chain of custody
The chain is every transfer of an item from recovery to court: who collected it, when, where, how it was packaged and sealed, and every subsequent handoff. Photograph the item in place before moving it, record the serial or identifying number, package and seal it, and document transfers at the time they occur. A break in the chain does not automatically suppress the item, but it gives the defense its argument and can cost the case.
Search warrants in DC
Title 23, Chapter 5 governs warrant applications. Your affidavit must establish probable cause and describe the place with particularity - the house, the floor, the apartment number. Return and inventory requirements must be met. The Comprehensive Policing and Justice Reform Amendment Act restricts no-knock entries to cases where sworn facts justify an exception and judicial authorization is expressly obtained.
Digital and forensic evidence
Riley requires a warrant for phone contents; a letter of preservation keeps provider records from being destroyed while the warrant is obtained. Document hash values and the tool used for extraction. Submit items to the DC Department of Forensic Sciences, the District's public forensic laboratory, in the packaging and manner required; do not open sealed envelopes sent from the lab. Be prepared for a defense challenge to a laboratory's accreditation.
Preservation obligations
The Innocence Protection Act (DC Code § 22-4131 et seq.) requires preservation of biological evidence in serious cases and provides a post-conviction DNA testing procedure. Treat evidence as permanent property of the case file, not as an item to clear from the property room.
Worked example
You recover a handgun under a car seat during a traffic stop. You photograph the firearm in position, note the serial number, unload it, package and seal it, and create an MPD property record under the case number and the arrestee's name. The firearm goes to DFS for latent prints and DNA; each transfer - officer to property, property to courier, courier to DFS - is logged at the time it happens. At trial, the record answers every handoff except the officer's own testimony, which covers the initial recovery.
Traps
Treating the chain as trial-only paperwork; commingling items from two scenes; assuming consent to search a phone because it was unlocked; failing to document the condition of an item before packaging.