Foster Bates appears at a post-conviction review hearing in Cumberland County Courthouse on Wednesday. He was convicted of murder in 2002 for the slaying of Tammy Dickson, but has maintained his innocence. Derek Davis/Staff Photographer

Two forensic science experts offered competing views Thursday on DNA evidence that was crucial to convicting a South Portland man who is seeking a new trial.

Foster Bates, 55, was found guilty in 2002 of the murder and rape of his neighbor, 22-year-old Tammy Dickson, in 1994.

Tammy Dickson

Bates has denied killing Dickson for nearly 30 years. Her body was found naked from the waist down, blindfolded, and had a green sock stuffed in her mouth. An autopsy said she died from asphyxiation, but investigators also believed she was raped, a point his defense attorneys are now questioning.

Bates is also pointing to DNA evidence collected from the sock as proof that he wasn’t involved in her murder and is hoping Thursday’s testimony will be enough to persuade Superior Court Justice Thomas McKeon to grant him a new trial.

He was allowed to present several pieces of evidence that the courts weren’t aware of during his first trial, including witness statements that pointed to a different suspect. But testimony from those witnesses was inconsistent Wednesday. One admitted she lied to investigators several times. Bates also has alleged that his attorney failed in 2016 to file a petition to consider the new witness statement promptly.

Testimony wrapped up Thursday afternoon. It’s unclear when McKeon will issue a ruling. He gave defense attorneys and prosecutors up to two and a half months to file written arguments and rebuttals.



DNA has always been central to Bates’ conviction. Prosecutors have said it’s what led them to him as a suspect.

Bates denied knowing Dickson during the investigation into her death, but after seven years he admitted that the two were having an affair when newer DNA technology found Bates’ semen in Dickson’s body.

Bates testified Wednesday that he lied about not knowing Dickson because he was scared the affair would draw extra attention from police – especially given that he’s a Black man and Dickson was a white woman. Prosecutors said the lie was an indication of Bates’ guilt.

In 2014, Bates’ defense team asked Superior Justice Roland Cole to consider a new DNA analysis that excluded Bates as a source on the green sock that had been forced into Dickson’s mouth, Cole later ruled the evidence wasn’t strong enough to merit another trial.

But in 2021, McKeon agreed to revisit the case.


Heather Coyle, who has worked in a forensic lab and teaches DNA testing at the University of New Haven, testified Thursday that semen samples, like the one found on Dickson’s body, are only detectable for up to five days. Coyle also said that there was no other DNA evidence tying Bates to the scene.

“It just shows sexual contact and nothing more,” Coyle said of Bates’ DNA. “It’s not necessarily related to the homicide. … Nothing else can place him at the scene.”

Jennifer Sabien, a forensic analyst for the Maine Crime Lab who tested Bates’ samples before his trial, said Thursday that Dickson likely didn’t shower or change clothes after having sex with Bates, which shortens the time from when her body was found during which semen would be detectable.

Coyle said Dickson’s injuries weren’t consistent with those of someone who is raped. Investigators at the time were likely biased by the assumption of rape, and it affected what evidence they chose to collect and test, Coyle said.

She said she wishes investigators had saved and tested more items from Dickson’s apartment that could have been directly linked to her murder, including a belt that police believed was used to choke her.

When the sock was tested after the trial, it showed that Dickson’s ex-husband, Anthony, was a potential match. But that DNA also could have come from their toddler son, who could’ve at one point touched the sock, or maybe his clothes came into contact with it in the laundry. No one ever tested the toddler to see if there was a match.


Bates’ attorney, Tina Nadeau, said in court Wednesday that the sock is one of several pieces of evidence they haven’t been able to locate.

Assistant Attorney General Donald Macomber pointed out Thursday it’s possible the killer might not have even left DNA on the sock. The killer could have been wearing gloves or left a sample so small it’s undetectable.

And even if Bates’ DNA wasn’t present anywhere else at the crime scene, Macomber cited other evidence that jurors considered during Bates’ trial in 2001, including the fact that Bates lied for seven years about their affair and that Dickson’s friends testified that she was scared of him.

“What would you draw from that?” Macomber asked Coyle.

“Scientifically speaking, I would say he’s a possibility,” she said. But looking only at the DNA results, “there are several other good male candidates that had semen left at the scene.”



Bates’ former attorney, Peter Cyr, also testified Thursday.

Cyr represented Bates from 2003 to 2019, handling most of Bates’ previous appeals and post-conviction review requests. After Cyr met in June 2016 with Amanda Indigo, who said she was in Bates and Dickson’s apartment building the night Dickson died, Bates almost immediately asked Cyr to file a petition for a new trial using Indigo’s statements.

Bates and Cyr only had a year to file a petition based on Indigo’s statements under state law. Bates wanted Cyr to file as soon as possible. Cyr filed the petition on June 12, 2017, less than 24 hours before the deadline.

Prosecutors argued that they believed Cyr and Bates knew about Indigo for far longer and the judge ended up dismissing the petition, alleging it was untimely, which Cyr still disputes.

Cyr lately withdrew from Bates’ case. Letters from the time vaguely reference a “conflict of interest.”

“Did Foster blame you for not filing a petition earlier than June 12, 2017?” Nadeau asked Cyr.

“I don’t know,” Cyr said.

“Did he ever express to you that he was very disappointed?”

“I don’t know that he expressed that about me, to me,” Cyr said.

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