Some possibilities were never pursued in the analysis of DNA evidence in the murder of Mabel Greineder because of changes in the standards used by the lab which examined the samples, a scientist admitted in the trial of the victim's husband, renowned Boston-area doctor Dirk Greineder.

Over the course of the investigation, several batches of evidence were sent to the Cellmark Diagnostics for testing. During that time, the lab changed its standards for how much genetic material needed to be found at certain locations on the DNA sequence, called alleles, for a positive identification to be reached.

"It was just too complicated and we made the decision that after (spring 2000) with a new submission we would stay with our new procedure," the scientist, lab director Robin Cotton said.

Defense attorney Martin Murphy pressed her on the point, repeatedly asking whether the lab's employees understood the stakes involved for Greineder, who faces life in prison if convicted of first-degree murder.

"Is it more important to you to follow (the lab's) standard procedures than to investigate whether alleles not matching the defendant or the victim were present in this case?" Murphy asked Cotton.

The day's testimony was rife with obscure terminology and complex descriptions of the procedures involved in DNA testing.

"Before you came to court and testified that this was the profile at the d3 locus on evidence item 29.1, you never evaluated whether that 19 that shows up in the electrotheragram on the right was real DNA or not?" Murphy asked in a typical question.

The Greineders were on a walk in a wooded park near their suburban home on the morning of October 31, 1999, when the victim was bludgeoned over the head with a small hammer and repeatedly stabbed with a pocket knife. Cotton testified Thursday that evidence recovered from the knife is similar to the doctor's DNA.

Prosecutor Richard Grundy claims that Greineder was living a secret existence marked by an obsession with pornography and trysts with call girls. He says the doctor killed his wife so that he could more freely pursue this clandestine life.

The defense claims that an unknown killer struck while the couple was separated during their walk. Murphy says that an amateurish police force unaccustomed to investigating homicides in the quiet suburban town quickly decided that his client was guilty and thus never pursued other leads.

Although the defense attorney has questioned most of the prosecution witnesses at length about the procedures they followed, his cross-examination of Cotton was particularly time consuming, lasting nearly six hours.

"Only twenty minutes more," Murphy quipped at the end of the day before quickly adding, "No only joking. Nothing further, your honor."

Testimony resumes Monday at 8:30 a.m.

The trial is being broadcast on Court TV.