Evidence Collection, Preservation, and Chain of Custody
Authentication and the unbroken chain
Evidence must be authenticated before it can be used; Ohio Evid. R. 901 requires evidence sufficient to support a finding that the item is what its proponent claims. Chain of custody is how you prove that. The core log fields: unique item number, description, date and time collected, location, collector, and every subsequent transfer with the receiving person's signature, date, time, and purpose. Package each item separately, seal it with tamper-evident tape, and have the sealer initial across the seal.
Photograph before you move anything; include a scale and a placard with the case and item number. Wear gloves. Do not test, clean, or "improve" an item. Digital evidence: preserve the original, work from a copy, compute and record a hash value, and capture metadata plus a screen recording of social-media pages including URL and timestamp.
Traps: back-dating a log entry; letting two items share one bag; letting an unlogged person - an intern or the client - carry the item; describing an item as "the knife" before it has been identified. Also remember that a gap in the chain usually goes to the weight the factfinder gives the evidence rather than automatic exclusion, but a cross-examiner will exploit it.
Rule of thumb: if you cannot narrate the history of an item from the moment you touched it to the moment it reached the courtroom without a single unexplained interval, your chain has a hole. When in doubt, document more than you think is necessary.