dissenting.
I respectfully dissent from the majority opinion in this case because I believe the district court erred in refusing to allow defendant adequately to argue or prove lack of knowledge that the gun possessed the physical characteristics which constitute a statutory “firearm.” Although the majority opinion characterizes defendant’s attempted defense as a “good faith” defense, I believe the defendant was also trying to establish his lack of knowledge that the firearm possessed the required characteristics to constitute a statutory firearm. I do not quarrel with the conclusion that it is not an adequate defense that the defendant is unaware of the law, but I do believe the government must establish, under Staples v. United States, 511 U.S. 600, 114 S.Ct. 1793, 128 L.Ed.2d 608 (1994), that the defendant had knowledge of the physical characteristics of the gun that the law uses to define what constitutes a statutory firearm. Thus, if the defendant knew that the gun was capable of firing projectiles, he would have adequate mens rea to be convicted even if he did not know that the law defined a statutory firearm as one capable of firing projectiles and even though he believed in good faith that he was not violating the law. However, he could not be convicted if he did not know that his gun either “will or is designed to or may readily be converted to expel a projectile by the action of an explosive.” I do not read the majority opinion as disagreeing with this standard. Thus, my difference with the majority is really in the application of that standard to the facts of this case.
Here I believe the district court ruled that defendant’s lack of knowledge of the characteristics of the gun was not material, and I think the court excluded important evidence that tended to establish the defendant’s lack of such knowledge. For example, defendant sought to elaborate upon his view that the gun could not function as a weapon and could not readily be made to function as a weapon, and that it was useful only as a lamp. Defendant further sought to have Lonnie Smith, his welding instructor at the local community college, corroborate this testimony. Additionally, defendant proffered testimony from Tim Kling, a former police officer familiar with firearms, regarding the state of defendant’s gun. Kling would have testified that a working gun such as that possessed by defendant would sell for between $150 and $250, whereas defendant sold the gun to Sandoval for $22. This evidence would have provided important support for defendant’s contention that he did not know he possessed
*1059a “firearm” as defined under the statute, Yet, the district court excluded this evidence.
I do not believe this excluded evidence can properly be characterized as “cumulative.” Although admittedly defendant did put on some evidence of his lack of knowledge, the proffered testimony of Smith and Kling was the only independent evidence that could have corroborated defendant’s contention that he did not know the gun possessed the physical characteristics of the statutoiy “firearm.”
I admit to some uncertainty about whether defendant’s conviction could be upheld under the “design” prong of the statutory definition of a firearm in 18 U.S.C. § 921(a)(3), which defines a firearm as “any weapon ... which will or is designed to or may readily be converted to expel a projectile by the action of an explosive.” (Emphasis added.) There is no doubt that the evidence in this case was sufficient to establish that the weapon possessed by defendant was “designed to ... expel a projectile by the action of an explosive.” Further, defendant did not proffer any evidence to dispute the fact that the weapon was so designed. He did argue that he planned, at some future date, to “redesign” the weapon by converting it into a lamp, at which time it would no longer be designed to expel a projectile. However, that redesign never occurred.
However, just like defendant did not focus upon the “design” definition of a firearm, neither did the government. Although the indictment included the “design” prong in the definition of firearm submitted to the jury, the government’s case was based largely on the other two prongs of the statutoiy definition. See IV R.O.A. at 77 (opening statement); Id. at 93 (testimony of Robert Sandoval); VI R.O.A. at 311, 315 (closing argument). Because this case was essentially tried on a statutory definition that the weapon was either capable of expelling a projectile or capable of readily being converted to expel a projectile, and because defendant was deprived of a fair opportunity to argue and prove his lack of knowledge of those particular characteristics of the weapon he possessed, I believe his conviction must be REVERSED and REMANDED for a new trial.