Can the defendant be convicted of robbery?
The defendant went to the victim’s house supposedly to look at and buy a rifle owned by the victim. When the victim gave the rifle to the defendant to inspect, he turned the rifle on the victim and refused to give the rifle back. Also, what would be a good argument that he can make so that he cannot be so convicted? Is it a good argument? Defend your answer.
Turning the rifle on the owner is the unprovoked and obvious threat gesture. You can be charged with robbery for the mere appearance or suggestion of a weapon coupled with a demand for property. A man with his pointed finger in a jacket pocket can be charged with robbery. So in this case, clearly, the threat was intentional and obvious with the goal of stealing property, which we assume was found in the defendant's possession.
The only defense he could use would be that no threat gesture existed, nor was any force used to enter the house or to acquire the gun. Since there are no witnesses (that your story suggests) or physical evidence other than possession, I could even suggest that I paid for the gun and it's simply my word against his.
If I have no prior criminal history, it would be a 50-50 chance of getting a conviction in a case like this. With priors for burglary and robbery or violent crime, it's more likely the DA would pursue it.
To me, it seems likely that the defendant can be convicted.
One definition of robbery is that it is the unlawful taking of something from one person's possession by force or intimidation. This seems to fit the definition. Assuming that the defendant held the rifle in a threatening way and that the rifle was (or the victim thought it was) loaded, that's force.
My defense would be twofold.
First, I'd try to argue facts -- I'd say the gun wasn't loaded and the defendant didn't threaten with it.
Second, I would argue that he did not take the gun by force. The gun was handed to him voluntarily and he simply refused to give it back. I would argue in that case for the much lesser crime of larceny.