When her best friend called 911 reporting her dead, the local crime scene investigators and coroner soon arrived at the Harper residence. The coroner did a preliminary exam at the scene, and determined that the first knife wound had apparently penetrated the aorta. This would explain the lack of significant bleeding at the site of the other knife wounds.
Severing of the aorta caused her to bleed into the abdominal cavity so fast that her blood pressure fell, and blood was not readily supplied to the other wound areas. Tom, who was sitting nearby appearing to grieve over his wife's death, heard the coroner tell the investigators this. He mused to himself that they had bought it, so far.
The CSI team finished their work hours later, but found little physical or trace evidence to go on. The murder weapon was found on the lawn, but wiped clean of prints. They sent it to the lab to be superglue-fumed for latent prints. Cast of the large shoe prints in the soft dirt were made, and a variety of fibers and hairs were bagged, but they all would turn out to be either those of Alice, Tom, or their son Alec, who was away at college.
A Lingering Suspicion
Still, to investigators it looked a little too clean--a little too perfect. Knowing that the husband is always a potential suspect in homicides, Harper cooperated with the police in all interrogations. A co-worker who was interviewed mentioned that Harper had worn a red flannel shirt the day of the murder. On a hunch, the lead CSI asked Tom for the clothes he was wearing that day. Since Harper was right handed and also wore his watch on his right hand, the watch was also collected. Harper did not see any problem with giving them these items; after all, he wasn't there at the time of the crime.
Newton Gets His Man
Dr. Harper, a distinguished dentist in the community, forgot a basic principle of physics: to every action there is an equal and opposite reaction. Yes, Newton's Third Law of Motion was about to spoil the good doctor's plan. Analysis of the red shirt at the crime lab revealed a radiating pattern of small mist-like blood droplets within the red fabric of the shirt. The victim was shot with a small caliber .22, which would only produce blood spatter for a distance of two or three feet. To get his shot positioned right to hit the aorta, Harper had walked up to within a foot of his wife before he pulled the trigger. Similar analysis of the watchband with Luminol and an ultraviolet alternative light source showed bloodstain on the band. A sample of this blood submitted for DNA analysis established that the blood was that of Alice Harper.
To solidify the case, they also found gunshot residue (GSR) on the shirt. The potential residue particles were lifted from the fabric with double sided tape, and then subjected to scanning electron microscope analysis. Now the victim's clothing and back were tested for GSR. GSR on Harper's shirt matched GSR removed from Alice Harper. One again, Newton's Third Law came into play in solving this crime.
The doctor's plan to commit the perfect crime was spoiled by a principle he learned in a high school physics class. But more important is that good forensic analysis provided the evidence necessary for another successful conviction.