M's child was born on June 9, 1983. Pursuant to ORS 109.125, she initiated filiation proceedings against F, alleging that he was the father of the child. The state intervened as a petitioner. F denied paternity. M testified that she and F had intercourse on one occasion, September 11, 1982. F admitted having intercourse but testified that it had occurred on the night of August 13-14, 1982. Both sides introduced the testimony of witnesses to corroborate their respective versions of when they had been together. A nurse practitioner who had examined Plemel testified that conception of the child would have been impossible in mid-August; she estimated that conception occurred between September 9 and September 16. M also called an expert witness Dr. E. W. Lovrien. Lovrien testified that: (1) the tests did not exclude the possibility that Walter was the father; (2) the probability that the tests would have excluded a 'falsely accused father' was 97.5 percent; (3) F's 'paternity index' was 178; (4) F's 'chance of paternity' was 99.4 percent; (5) F's 'chance of nonpaternity' was 0.6 percent; and (6) it was 'extremely likely' that F was the father. The last three statements were essentially equivalent to, and derived from, the paternity index. F, by a motion in limine, sought to exclude that portion of Lovrien's testimony related to the paternity index and its equivalents. He argued that the testimony was irrelevant because the 'probability of excluding a falsely accused father' provided the jury with all of the information that could be obtained from the blood tests. The argument was premised on his contention that in order to derive the paternity index, Lovrien had made an arbitrary assumption about the strength of the other evidence presented in the case. The trial court, without stating its reasons, denied Walter's motion in limine and overruled his objection. The Court of Appeals affirmed, holding that the testimony regarding the paternity index helped the jury to interpret the blood test results and that Lovrien's testimony minimized any potential for jury confusion by clearly explaining the limited significance of the statistics he presented.