As far as I am concerned, the only issue in the Jodi Arias trial is has the government proven premeditation. That of course, is important because if the government has not proven premeditation, they cannot convict her of murder in the first degree and thus the death penalty is off the table. And while the government has also alleged murder in the first degree by way of felony-murder, that allegation is so specious as not to even warrant a response.
The government has not proven premeditation, and in fact, could not do so under any circumstances. Without direct evidence, either a confession by Ms. Arias that she intended to kill Mr. Alexander, as in "I wanted to kill to him", or an overt act such as hiring a hit man or waiting in wait in ambush, the government cannot prove premeditation beyond a reasonable doubt. Note that I am not saying she did not intend to kill him or that there is not very good reason to suspect that she intended to kill him, just that the government will not be able to prove it beyond a reasonable doubt. And that has been clear since day one. Someone asked me on twitter a question along the lines of "she lied so she doesn't get the death penalty?". My answer, yes, exactly right. To paraphrase Lt. Kaffee from a "Few Good Men", it doesn't matter what we know; it only matters what we can prove.
Instead of proving premeditation with direct evidence, the government is trying to do so with circumstantial evidence. So far the attempt has been, with the most charitable interpretation possible, pathetic. While the law does not recognize a distinction between direct and circumstantial evidence, there is a jury instruction that says exactly that, the inference the government wishes the jury to draw from the circumstantial evidence is, dare I say, comically lacking.
If they could have proven the gun that Ms. Arias used to shoot Mr. Alexander was in fact stolen by Ms. Arias then that would be very good evidence of premeditation. But they have not done so; nor are is the government able to do so. On cross examination, the government has asked her number of questions regarding gas cans. This could be fruitful to the government's allegation of premeditation, but the prosecution has not closed the loop on this point.
In particular, my assumption is that there trying to prove Ms. Arias used gas cans to avoid being seen in Arizona at a gas station by either a witness or cameras. That, if true, would show planning of at least something. So why then didn't Mr. Prosecutor flat out ask Mr. Arias if that was her intent? Instead, he avoided asking her that question because of one thing: fear. Mr. Prosecutor is afraid she will have an answer for the question and the jury will believe her. So he is instead doing what trial lawyers have been trained to do, save the ultimate question for closing argument when the other side has no chance to contradict your argument.
Under all circumstances, such a approach is cowardly and craven. In the particular circumstance of this one in which a prosecutor's job is not to win per se but act as a "minister of justice", it is downright evil. When someone, anyone, as in Jodi Arias, is on trial for her life, she should be given every opportunity to directly answer all the government's accusations in her own voice directly to the prosecutor's face. It should then be up the jury to decide who to believe with all the facts before them. The jury should not be in the unfortunate position of deciding the fate of a person, as they are in now, without all the facts before them because the prosecutor was too afraid to ask the defendant the ultimate question.
But assume for the sake of argument she was asked that question and did not have a good answer for it. What was she planning? Was she planning on killing him since the moment she asked to borrow the gas cans in May, or since she left for her trip from California? If she was planning on killing him before she left on her trip, then why did she stay with him for 8 hours and have sex with him on the same day? Does that really sound like a plan on murdering Travis Alexander? I don't know, and even more more importantly, the government cannot answer these questions without speculation or guess work. The guesses may be reasonable and even probable, but that is not proof beyond a reasonable doubt, and certainly not proof enough to send Ms. Arias to death row.
As far as whether her testimony is believable, she was not untruthful in the sense she was deliberately testifying falsely. She believes what she is saying. While it may not be in fact what objectively happened, I have no doubt that she either always believed what she is saying since day one, or in the 5 years since Mr. Alexander's death has convinced herself of what she is saying is true (this is called the "narrative fallacy" made famous by Nasim Taleb in "The Black Swan"). By way of example, Sarah Palin says she doesn't believe in evolution and thinks the Earth is only 5000 years old. Those statements are nothing short of ridiculous, completely contracted by all scientific evidence, and obviously not true, but she is not a liar because she honestly thinks those are the facts.
As far as the numerous accusations she was being evasive or deliberately forgetful, in that regard her testimony is no worse than the typical police officer testifying on cross "I don't remember, I don't recall, or I don't know", something that I have personally experienced dozens of times.
That being the case, it is obvious that the government overcharged her and should have accepted her offer to plead guilty to murder in the second degree some time ago. That way, the government could have avoided this silly fiasco that has hardly made Arizona look civilized and respectable, ie, "bull dog" or "mad dog" prosecution. Once the jury comes back with something less than a conviction for murder one, I hope media will aggressively question the Maricopa County Attorneys' Office why they wasted so much time and money on a wasted prosecution. I hope they will ask MCAO why did they refuse to accept Ms. Arias' plea to murder two with the hopes of garnering fame and attention? While nature may be "red in tooth and claw", do we want that to be the philosphy of our prosecutor's office?