Orange County Circuit Judge Marc L. Lubet threw out police interviews and evidence gathered in a search of Lisa Nowak's car.
He said investigators took advantage of the astronaut, who had not slept for more than 24 hours before the alleged airport attack of a rival for a fellow astronaut's affections. The case prompted international headlines in February.
Police Detective Chris Becton answered evasively when Nowak asked about an attorney, and had not read her her legal rights before he started questioning, Lubet said.
"Detective Becton failed to answer defendant's question regarding whether she needed an attorney in a truthful and straightforward manner," Lubet wrote.
"He made threats and used coercive psychological techniques," Lubet wrote of Becton's more than six-hour jailhouse interview.
Becton testified at pretrial hearings that Nowak was hardly a sleep-deprived, confused suspect. He characterized Nowak as a cunning suspect who bargained with information in an interview similar to a "chess match."
Lubet's order was entered late Friday, prosecutors did not immediately responded to requests for comment.
In a statement, Nowak lawyer Don Lykkebak said, "We are extremely pleased and gratified that Judge Lubet has granted the motions to supress both Lisa Nowak's statement and the evidence taken from her car last February.
"Judge Lubet's learned order explains clearly why the statement and evidence was illegally obtained when he states that 'whether a prince or pauper' the constitution protects everyone equally," Lykkebak said.
Nowak was arrested after allegedly confronting Colleen Shipman, the girlfriend of former space shuttle pilot Bill Oefelein. Authorities say Nowak drover all night from Houston, stalked Shipman at the Orlando airport and tried to get into her car, then attacked her with pepper spray. Shipman was able to drive away.
Nowak's BMW was parked at an airport-area hotel. The search yielded maps to Shipman's home, large garbage bags, latex gloves, a list with Oefelein's computer passwords, e-mails between Shipman and Oefelein and a handwritten letter to Oefelein's mother believed to be from Nowak.
Also in the car was a receipt for a hotel in Defuniak Springs under a different name - Linda Turner - and the diapers that provided one of the case's more bizarre allegations.
Becton noted them in his report but never entered the diapers into state's evidence. Nowak's defense steadfastly denies she ever wore or urinated in them to avoid stopping, but Becton said he found two soiled diapers that Nowak told him she used on the 1,000-mile drive from Houston.
Lubet's ruling was a big win for the defense, but it did not extend to items seized from the duffel bag Nowak was carrying - a steel mallet, buck knife, BB gun resembling a real 9mm handgun, gloves and rubber tubing.
Nowak's trial is scheduled to begin April 7, and her attorney, Donald Lykkebak, is expected to use a temporary insanity defense. In court papers to that effect, Lykkebak said Nowak suffered from major depression, obsessive-compulsive disorder, insomnia and "brief psychotic disorder with marked stressors.