Forensic Analysis

Potential errors in the use of medical specimens in courtroom setting

Case Report:

The patient was a 22 year old man involved in a T-bone type automobile collision with several fatalities. He was the driver of the vehicle that was initially thought to have run a red light and struck the second vehicle on the passenger side,

During the collision he had suffered significant lower extremity trauma with significant soft tissue injury but no significant blood loss. Admission blood studies revealed a hematocrit of 52%, well above the ‘normal' 32-38%.

Later, witnesses suggested that he most likely had the right-of-way, but he was charged because the results of the blood alcohol testing, performed in the hospital, showed a serum ETOH of .11 gm/dL which was interpreted to indicate impairment, using the ‘standard' conversion factor of serum-to-whole blood ratio.

According to that calculation, the conversion factor of 1.3:1 (which assumes a normal hematocrit), the whole blood alcohol was determined to be .08-.09 gm/dL.

Because the actual blood studies performed on admission indicated that the hematocrit in this particular individual was the not in the ‘usual normal' range, it could be shown that the conversion factor should actually be 2:1 since the serum actually made up 50% of the sample.

Using this information, the blood alcohol calculation resulted in a level of 0.05 gm/dl. This finding was clearly under the ‘legal limit' and serves as an indication that the assumptions made in the original calculation were not supported by scientifically valid data.

Consequently the numbers were properly argued to be inadmissible in the court. The case settled prior to trial with reduced charges.

Comment:

It is common practice to introduce the results of hospital laboratory tests into courtroom proceedings with the premise that those tests—irrespective of the potential problems with chain-of-custody and confirmatory testing procedures—are to be regarded by jurors as ‘scientific fact'.

In actuality, the tests were not accurate as they were purported and lacked the critical parameters required for presentation in a legal setting, as scientific evidence. The standard requires confirmatory testing by a second method and verification of chain-of –custody for the specimen. Both are frequently absent in ‘hospital testing' methods, which frequently involve only screening procedures, and rarely have documented chain of custody data.

Consequently, the assumption that these test results are admissible as scientific data need to be carefully scrutinized in cases both in the criminal and civil justice systems.