ALFRED — A scientist who was scheduled to testify in the murder trial of Derek Poulin but couldn’t attend would have told jurors that Poulin’s father had a possible blood mark on his shoe that police never tested, lawyers told the court Thursday.

Jennifer Smith, a scientist who works for Cellmark Forensics in Texas, was scheduled to fly in late Wednesday from Dallas to testify Thursday, but her flight was canceled as remnants of Hurricane Bill lingered over the southern part of the country.

Smith was to appear as a defense witness on the final day of testimony in Poulin’s trial in York County Superior Court, where he is accused of murder and arson in the death of his grandmother, 61-year-old Patricia Noel, in her Old Orchard Beach home on Oct. 23, 2012.

Poulin’s attorney, Amy Fairfield, said before the trial began that Poulin’s father, Reginald Poulin, could be viewed as an “alternate suspect” in the case and the shoe evidence bolsters that argument. Both Poulin and his father, who is Noel’s son, lived with Noel in her home at 44 Wesley Ave. in Old Orchard Beach at the time of her death.

The prosecution’s case against Poulin is based entirely on circumstantial evidence. Noel’s DNA was found on a reddish-brown stain on the toe of Poulin’s boot. Poulin’s statements about where he was at times on the day of her death do not match purchase receipts found in his car. The clothes Poulin turned over to police for examination do not match the clothes he was seen wearing in security camera footage from that day at the Bureau of Motor Vehicles in Portland.

Poulin, 26, is accused of bludgeoning his grandmother to death with a golf club and crescent wrench, stabbing her about 70 times with a knife and then setting her body and house on fire. The heat from the fire was so intense that much of the evidence was destroyed, and investigators found no conclusive fingerprints or DNA on the murder weapons.

Neither Poulin nor his father testified before the jury during the trial. Poulin told the judge out of the jury’s presence Thursday that he decided against testifying. Reginald Poulin, 45, told the judge outside the jury’s presence Monday that if he was called as a witness he would use his Fifth Amendment right not to testify on grounds his testimony could incriminate himself, though prosecutors said they don’t have grounds for a case against him.

Prosecutors and defense attorneys prepared a written statement for the jury saying that, had she appeared, Smith would have testified that she tested Reginald Poulin’s shoes at the request of Fairfield, Poulin’s attorney. A mark on the sole of one of the shoes tested “presumptive positive” for the presence of blood, Fairfield told the jury.

That evidence is a possible blow to the prosecution, because police focused early on Poulin as a suspect and never seized clothes or shoes from his father for testing after Noel’s death. A private investigator hired by Fairfield collected the father’s belongings more than a month after the homicide and sent them for testing at a private lab.

The defense rested its case later Thursday after calling a total of eight other witnesses.

Lawyers are scheduled to make their closing arguments Friday morning. Justice John O’Neil Jr. told jurors they can expect to begin deliberations before noon.

Much of both the prosecution’s case against Poulin and his defense, that his father could have done it, come down to timing.

Poulin told police that he last saw Noel around 11:30 a.m. on Oct. 23, sitting in the kitchen of her home with a cup of coffee and a cigarette.

Poulin said in a recorded interview with police that night that he spent the afternoon in Portland visiting his mother and running errands.

Noel’s neighbor from across Wesley Avenue called 911 at 2:09 p.m., and firefighters discovered Noel’s charred body inside after extinguishing the fire in her bedroom.

Surveillance camera footage and receipts from the Bureau of Motor Vehicles show that Poulin entered the Portland office at 2:50 p.m. and left at 3:08 p.m. after purchasing a replacement driver’s license. Poulin later went to a dental clinic in Portland, where records show a staff member entered an appointment for him in the scheduling computer at 4:22 to have a cavity filled later in the week.

Poulin’s mother, Cathleen Emery, testified that her son learned in a phone call with Reginald Poulin around 4:20 p.m. that Noel had died. Phone records confirm that call between Emery’s cell phone and Reginald Poulin’s phone.

Poulin stopped at a Catholic Charities thrift shop in Portland and made a $5 clothing purchase at 4:56 p.m. before driving to Old Orchard Beach, where he arrived at 5:33 p.m.

Reginald Poulin was at work for most of the day driving a route in Yarmouth and Falmouth for a lawn care company, spraying pesticides and fertilizer.

Computerized records from the company’s Portland headquarters indicate Reginald Poulin clocked in at 7:02 a.m. and clocked out at 3:44 p.m., past and present managers from the company testified.

But the managers for Lawn Dawg also testified that computerized logs that Reginald Poulin entered from his service truck that day show he finished his last job at 12:22. His past manager there, Patrick Devou, testified Thursday that the GPS system in the truck that day was switched off.