The challenge for the civil case has always been the court-created immunity doctrine. If it couldn't get past that barrier, there would be no discovery phase, no opportunity for a fishing expedition, no chance to file a motion in limine to protect Morphew from difficult lines of inquiry, no chance to hone his story and explain away all the lies, the trash dumps, the phony work project, and the telemetric data.
The voluminous complaint was designed to create the appearance of a mountain of provable facts showing bad acts by investigators and prosecutors, with the hoped-for disciplinary decisions adding outside credibility to their claims. If they were lucky, such a complaint could burden a busy judge or magistrate to the extent that he or she would rely on the alleged bad acts and deny the motions to dismiss and let the discovery phase begin - reasoning that immunity could be raised at any time and the abused plaintiff deserved at least a chance at discovery. Dismissal at the outset is an extraordinary remedy, after all.
I speculate that the attorneys may have failed to note that, for purposes of the motion to dismiss the judge could rely on the arrest affidavit attached as an exhibit. The judge was able to align its allegations with the enumerated facts alleged in the body of the complaint and discern that Morphew did not contest the affidavit in its entirety. Concluding that the uncontested facts in the AA were sufficient to establish probable cause for Morphew's arrest, he invoked immunity to dismiss the case.
I think the civil case arises in part from the attorneys' sense of mission, in part from Morphew's hubris, greed, and desire for vindicating headlines, but mostly from the real malfeasance, misfeasance, and nonfeasance that led to adverse rulings in the criminal proceedings. They gave these zealous attorneys (who have had success in other cases) hope that that the high court will abrogate or limit its immunity doctrine as unjust in the face of manifest wrongdoing. It's a long shot, but the attorneys knew they'd face it sooner or later.
I note that the 12th District investigators and prosecutors are taking a very low public profile and Suzanne's family are, too. They don't want to be part of Morphew's public circus for good reason. They don't want to feed his publicity campaign, but strategically, they want to have Morphew's story on the record under oath before they file (they will have a better opportunity to counter it), and they don't want even the appearance of impropriety to affect their case.
On the question of the Fruit of the Poisonous Tree Doctrine, there is no reason to believe it will apply. I can't remember any arguments in the 11th JD case that evidence should be suppressed because it was illegally obtained. The arguments were about sanctions for discovery violations, the credentials of experts, and in at least one case, about the balance between the value of an expert's testimony to the jury versus unfair prejudice to the plaintiff.
Morphew may argue in the new case that his previous statements to investigators should not be admitted because he was unfairly interrogated, but that would be a new argument that once again, flies in the face of existing precedent. There is no question the Morphew's statements were voluntary, and investigators are allowed to lie about the evidence they have in order to secure adverse statements and confessions from the subject.