Oregon Revised Statutes Domestic Relations § 109.254

(1) The tests shall be made by experts qualified as examiners of genetic markers who shall be appointed by the court or administrator, as defined in ORS 25.010. Any party or person at whose suggestion the tests have been ordered may demand that other experts, qualified as examiners of genetic markers, perform independent tests under order of the court or administrator, the results of which may be offered in evidence. The number and qualifications of such experts shall be determined by the court or administrator.

(2) The blood test results and the conclusions and explanations of the blood test experts are admissible as evidence of paternity without the need for foundation testimony or other proof of authenticity or accuracy, unless a written challenge to the testing procedure or the results of the blood test has been filed with the court and delivered to opposing counsel at least 10 days before any hearing set to determine the issue of paternity. Failure to make such timely challenge constitutes a waiver of the right to have the experts appear in person and is not grounds for a continuance of the hearing to determine paternity. A copy of the results, conclusions and explanations must be furnished to both parties or their counsel at least 20 days before the date of the hearing for this subsection to apply. The court for good cause or the parties may waive the time limits established by this subsection.

(3) An affidavit documenting the chain of custody of the specimens is prima facie evidence to establish the chain of custody.