Defendant argues WI child porn law unconstitutional; if you're texted CP and open it, are you guilty of possessing CP?

Could someone texting you child porn, a text you unwittingly open, get you charged with a felony? Also, is it fair to charge adult males with child porn possession but not the underage females that texted the images to them, if they both technically possess child pornography? The case below raises both issues.

In State v. Perino, No.'s 2012-CF-0217, 2012-CM-0116 (Wis. Cir. Ct. filed Jan. 18 & Feb. 23, 2012) the defendant is charged with two counts of possessing child pornography (2012-CF-0217 - link has case history) and two counts of sex with a minor over age 16 (2012-CM-0116). In March of 2013, the defendant filed three motions to dismiss based on the following: (1) that the charged statute (Wis. Stats. § 948.12, see infra) is unconstitutionally vague and overbroad, as applied; (2) that the images are not "lewd" as required by the statute; and, (3) that the prosecutor is selectively prosecuting the case.

Copies of the Wisconsin Circuit Court documents:

1. Defendant's Motions
2. Prosecutor's Responses

The defendant was later indicted in federal court, as well, where he was "charged . . . with one count of producing child pornography and [the indictment] refers to two victims A and B. Four other counts appear to refer to the same former student in the state charges, and a sixth count seeks forfeiture of Perino's computers and cellphone." (Vielmetti, infra). You can find the indictment, here: E.D. Wisconsin Perino Indictment

State of Wisconsin Case

Wis. Stat. § 948.12 states:

948.12  Possession of child pornography.
(1m) Whoever possesses, or accesses in any way with the intent to view, any undeveloped film, photographic negative, photograph, motion picture, videotape, or other recording of a child engaged in sexually explicit conduct under all of the following circumstances may be penalized under sub. (3):
     (a) The person knows that he or she possesses or has accessed the material.
     (b) The person knows, or reasonably should know, that the material that is possessed or accessed contains depictions of sexually explicit conduct.
     (c) The person knows or reasonably should know that the child depicted in the material who is engaged in sexually explicit conduct has not attained the age of 18 years.

Bruce Vielmetti has a good synopsis of the case in his Journal-Sentinel article - Lawyer wants girl charged for nude photos she sent to teacher:

The attorney for a former Hales Corners teacher facing charges he had sex with a female student has asked a judge to charge the girl with distributing child pornography - for sending nude photos of herself to the teacher.
...
Craig Perino was charged in Racine County in January 2012 with two counts of sex with child 16 or older, both misdemeanors. According to the complaint, he and the girl had encounters last year at his home in Waterford that involved drinking and intercourse.
A month later, prosecutors added two counts of possession of child pornography, both felony offenses, after nude photos of the girl were found on Perino's phone and computer. He has pleaded not guilty to all the charges.
…
Perino's attorney, John Birdsall, has moved to dismiss the child pornography charges on several grounds. He argues the statute is unconstitutionally vague and overbroad because it makes anyone who might open and view an unsolicited texted or emailed image of child pornography subject to criminal prosecution. 

Birdsall also argues that the texted photos, while nude, are not "lewd" under the statute. 

Finally, Birdsall asks that the charges be dismissed because they represent selective prosecution. His motion notes that the girl was 17 when she reported her sexual encounters with Perino and is 18 now. If the prosecutors believe the images amount to child pornography, the girl should be charged as an adult with producing, distributing and possessing them, the motion states.
…
Refusing to charge the girl, Birdsall argues, amounts to an admission by prosecutors that the images are not in fact lewd under the Wisconsin statute and therefore don't support the child porn charges against Perino.
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In his responses to Birdsall's motions, Assistant District Attorney Robert Repischak argued that the issues were raised too late, that the question of whether the photos are lewd is one a jury should decide, and that Perino's constitutional challenge relies on hypothetical situations that differ from his own. 

"The defendant seemingly forgets" that he told an investigator he had stored images on his employer's computer and deleted them once he learned of the investigation and that he "clearly . . . was not an unwitting recipient of the images at issue," Repischak said in his written response to the motions.