The tips and insights we received from all you wonderful bloggers helped crack this cold case wide open. Even to a seasoned conspiracy theorist like myself, the answer to this riddle blew my mind.  After extensive interviews and detailed examination of all the forensic evidence, all the arrows pointed to Professor Putnam Cowley. Although the Ford Tempo yielded a veritable bounty of suspects who fit the height range of the driver, it was this very analysis that helped us zero in on the crafty professor. He was the only one of the four who could have left key pieces of trace evidence on the victims. For all you cats and kittens who didn't reach this conclusion, here's an explainer:

 The Beech Blight Aphids found on Clotilde Eames seemed to point to Nestor Pope's guilt since he worked in an area infested with them, and he was the only suspect we could find who was in direct contact with the insects outside. The key word here is outside. Bug reminded everyone, though, that during a Beech Blight Aphid infestation, the little critters can work their way inside, invading other fauna. He also reminded us that the maturity of the aphids found on Clotilde were a bit advanced for the time of year and the weather conditions. Their mature stage wouldn't be unusual, however, if the aphids came from a warmer, indoor environment. If you recall, Professor Cowley was re-interviewed as he tried to water the many ferns in his town home. It's possible these ferns were a source of the insects. Professor Cowley, therefore, became a viable suspect based on the aphids.

 Segmental analysis on the hair strand found on Dr. Amy Tropos' coat revealed it belonged to someone who had ingested morphine sulfate for two months. Given Dr. Derek Douglas' painkiller abuse, presumably the hair came from him. DNA testing, however, proved it didn't. Assuming the hair came from the killer, the person most likely to have used morphine sulfate - a prescription narcotic - was Professor Putnam Cowley, because of his lung cancer. Due to the spread of the cancer to his bones, Professor Cowley was experiencing pain so intense that occasionally, Clotilde Eames stayed over to help nurse him through the night. Undoubtedly, Professor Cowley was treated with some type of pain medication. It was recently confirmed that morphine sulfate had been prescribed to him in January, 2002.

Early this morning, the Boston police entered the town home of Professor Putnam Cowley with a search warrant. They found the professor on a stepladder in his kitchen, searching for a jar of peanut butter. Evidently, his previous use of a wheelchair was just a ploy to throw off the renewed murder investigation. Hidden in the back of a broom closet, the police found a pair of Dr. Marten oxford shoes with traces of dried blood. In a large fern planter, they found a 9mm gun buried in the soil. With these discoveries, Professor Cowley, the Classics scholar, confessed to the murders of Leigh Chasa, Clotilde Eames, and Dr. Amy Tropos. Shortly before their deaths, he was diagnosed with terminal lung cancer and given only six months to live. Angry with this fate, he sought revenge on The Fates, three women of Greek mythology - Clotho, Lachesis, and Atropos - collectively known as The Moriae, who were attributed with having the power of deciding a man's destiny, primarily how long a man lives.

Professor Cowley, in his disturbed state of mind, associated the names of his three victims with those of the three Fates. He thought that by killing them, he could reverse his own death sentence. Professor Cowley frequented the Le Chasas cafe in Beacon Hill where he encountered Leigh Chasa, and he passed Dr. Amy Tropos in the halls of Boston General hospital during his many appointments, noticing the name on her I.D. badge. He stated that killing Clotilde Eames, his research assistant, was the most difficult thing to do because of their friendship, however, he felt it was essential for his own survival. 

In 2005, on the third anniversary of the Beacon Hill murders, Professor Cowley sent the mysterious letter with the bloody numeral '3' to the morgue as a sign of his victory over death. A court-appointed physician who reviewed Professor Cowley's medical records shortly after his arrest this morning felt that the spread of Cowley's lung cancer to his brain in 2002 may have affected his mental state. Of note is the fact that recent CT scans reveal no trace of cancer remaining in Professor Putnam Cowley's body.