Evidence At A Murder Trial

[evandavis]

Here is the situation: An elderly woman shares her home with her son who does not pay rent. The elderly woman gets up one day and finds her neighbor in her closet dead from a stab wound with the knife still in his back. she calls 911 the police arrive and the ambulance takes the elderly woman to the hospital for observation because she is in shock.
The police canvass the neighborhood and talk to the dead mans wife who says that the elderly neighbors son has been in there house several times uninvited and has attempted to climb into her bed several times.
In the elderly womans home they collect evidence from her sons bedroom a blood fingerprint adjacent to a light switch is found, using an amino acid stain, after locating the print using the absorptive properties of blood and a portable argon laser. Turns out the fingerprint belongs to the right index finger of the son and the DNA is from the dead man.
Based on this evidence the police have an arrest warrant issued and the son is arrested.
How would the lawyer file to have the evidence excluded? and based on what case laws?
Can the lawyers argue fruit of the poisonous tree doctrine for this based on the dead mans wifes statements? did the police violate the fourth amendment by searching the sons room since the crime didn't take place in that room and they did not get a warrant to search it?
Any help with court cases or some advice on how to procede would be greatly appreciated.