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Chain of Custody
Definition: Chain of custody, in legal contexts, refers to the chronological documentation or paper trail, showing the seizure, custody, control, transfer, analysis, and disposition of physical or electronic evidence.
Now how can this relate to DUI cases? Because, in order for a DUI blood test result to have any evidentiary value in court, a proper chain of custody must be kept. The prosecution must lay a proper foundation in order to admit blood test results in court.
Chain of custody documentation must be maintained at all times, and the chain of custody must remain intact. In forensic science, the specimen label, specimen envelope, and the laboratory’s internal chain of custody all help establish the integrity of the specimen. The Federal Government requires that their standardized Custody Control Form be used, and the control and accountability of specimens be maintained at all times. Regardless of the agency, the requirements are universal: every individual in the chain must be identified, and the date and purpose for access to the specimen must be documented by the individual handling the specimen. Since the chain of custody begins from the start of the blood draw, procedures must be established to safeguard the identity of the specimen vial and to prevent any possible mix-up of specimens in multiple-draw situations. Proper chain of custody documentation shows who handled the specimen and where the specimen was located at all times, using the “Z formation.” The Z formation is named because of the zigzag path the chain follows. That is, the format states that custody goes from A to B, from B to C, from C to D, etc. Thus, the Z formation always has the same name or location in the “to” entry as in the immediately following “from” entry.
Proper Chain of Custody; Z Formation
Improper Chain of Custody
The improper chain of custody leaves gaps in the chain. The example in this chart begs the following questions:
- What did Mary do with the blood?
- Did Mary put the blood in the secure refrigerator?
- When did Mary put the blood in the refrigerator?
- Did Mary leave the blood on a counter top for several days?
- Where was the blood between 1/1/04 and 5/7/04?
How Can Chain of Custody Gaps Be Useful for a DUI Defense?
Any time the blood sample changes hands; a document must be signed and dated, with the time of receipt acknowledged. This is to ensure that someone is responsible for the sample at all times, to prevent any chances of tampering with the evidence. Some state statutes specify where the blood sample is to be kept and stored during transport, as well as the timing requirements. If a sample does not comply with the statute’s procedures, the judge may determine the BAC results to be inadmissible. Additionally, the prosecutor may even decide to dismiss the case.
For a sample to be admissible, the prosecution bears the burden of establishing:
- The person who drew the blood;
- That the person who drew the blood was qualified to do so;
- The time and location the sample was taken;
- The circumstances under which the sample was obtained;
- The laboratory technician who analyzed the sample;
- The qualifications of the lab technician;
- That the sample was accounted for the entire duration of testing
- That the testing instrument the sample was analyzed on was properly calibrated and maintained;
- That the method of testing was an established method commonly accepted in the field;
- That the sample was properly preserved and stored prior to testing and during transport.