Johnson's work since 2003 has focused primarily on consulting on legal cases, with some consulting on labs, she said. She has only testified on behalf of the prosecution one time, she added.
When asked how much the defense was paying her to consult on the case, Johnson said she was being paid $250 an hour before her testimony and $2,000 a day for the two days she was on the stand. She estimated her bill to the defense will be around $6,000 to $7,000.
On the one known study that has been done on how the blood tests react with blood exposed to the elements, Peuvrelle noted trace amounts of blood were still found accurately with the tests.
Johnson replied that the blood tested in the study was not aged 20 years.
Peuvrelle asked if she knew whether the blood had been in contact with or buried under soil, covered by a deck, blocked on one side by a house or blocked on one side by lattice work.
Johnson said, to her knowledge, these were not factors in the study.
When it came to the email Johnson sent Christian Stadler, a German scientist who works for the company that manufactures the blood test used by Butler, Peuvrelle noted the parts Paul Flores' defense attorney left out.
According to the email exchange, there are no validation studies pertaining to the test's ability to accurately read samples exposed to soil for more than 20 years.
"Generally, I would say that after 20 years there is no hemoglobin left due to degradation. Maybe in a dry desert on shady place," Stadler wrote to Johnson.
He added the test could react "invalid" if the pH is too high or too low, but the buffer that is required to be used with the test should prevent that outcome.