State v. Kurt J. Doerr, 229 Wis.2d 616, 599 N.W.2d 897 (Ct. App. 1999)
For Doerr: John M. Carroll
Holding: A preliminary breath test (unlike certain other breath test instruments) requires expert testimony to explain its import:
The PBT device has not been approved by the DOT and does not receive a prima facie presumption of accuracy to establish a defendant’s blood alcohol level. Therefore, prosecutors who wish to rely on the PBT results are required to present evidence of the device’s scientific accuracy and reliability and prove compliance with accepted scientific methods as a foundation for the admission of the test results.
The state didn’t lay a proper foundation for its witness to testify about the PBT results. The error, however, was harmless.