Even though he was HIV-positive, his drug-treatment regimen helped make the risk of spreading the disease through unprotected sex “immeasurably small.”

That was the picture painted Thursday by a defense expert testifying on behalf of Robert W. Richardson II, a Lawrence man on trial this week for allegedly exposing four women to HIV in the past year.

Clifton Jones, a Topeka physician who specializes in infectious diseases, cited a study done in Uganda that found there was no transmission of the disease during sex for people with less than 1,500 copies of the virus in their blood – and that the chance of spreading the disease through sex at that level was less than 1 in 10,000.

Richardson had fewer than 50 copies of the virus at one point in November 2005, according to testimony. At that level, Jones told jurors, “it seems probable” there would be no risk of exposure through sex, though he said he couldn’t prove it.

Assistant Dist. Atty. Amy McGowan said even though spreading the disease would be rare at that level, “Rare doesn’t mean no risk, right?”

“That’s correct,” Jones said.

Today will be the third and likely final day of testimony in Richardson’s trial in Douglas County District Court. Prosecutors rested their case at midmorning Thursday, and defense attorney Thomas Johnson then began calling his witnesses.

An alleged victim who had an affair with Richardson while the two were working at the Kansas Department of Health and Environment testified Thursday she was “shocked” when she learned through media reports that Richardson was HIV positive.

According to testimony, Richardson sometimes explained his health problems by saying he had a heart condition – at least, that’s what it sounded like he was saying.

Attorney Johnson has suggested that Richardson really was saying he had a “H.A.A.R.T.” condition – an acronym meaning “Highly Active Anti-Retroviral Treatment” – which was his way of describing his regimen of HIV-treatment drugs.