By Laura Jarrett, CNN

(CNN) -- "Is it relevant?"

A frequent refrain from the federal judge overseeing Sen. Bob Menendez's bribery trial, as he presses the lawyers to show him why he should admit or withhold certain evidence from the jury.

For 18 days, 12 jurors and six alternates have dutifully showed up to a federal courthouse in Newark as the Justice Department tries to prove the New Jersey Democrat engaged in a years-long bribery scheme with a wealthy doctor from Florida.

The men deny the charges and the trial -- now in its seventh week -- will soon turn to the defense as they try to convince jurors that prosecutors have wrongly twisted a 25-year friendship into a federal crime.

But Judge William Walls, the self-described "gatekeeper" of evidence at trial, has already shielded the jury from certain testimony, a number of documents, parts of a CNN interview and a section of the senator's own website.

Here's a look at some of the more potentially compelling evidence the jury will never see.

Home-state senator

A key point of contention at trial is the meaning of a "constituent." Prosecutors accuse Menendez of accepting bribes from Dr. Salomon Melgen, a wealthy ophthalmologist in Florida, in return for political favors.

Last week prosecutors sought to introduce a screenshot of the "frequently asked questions" section on Menendez's Senate website, which states in part: "if you are not a New Jersey resident, I will refer your inquiry to your home state Senators."

"The relevance of this document is that Dr. Melgen, of course, lives outside of New Jersey," said prosecutor Peter Koski, in the hopes of casting doubt on any suggestion that the senator was merely assisting a constituent with business disputes.

Yet defense attorney Abbe Lowell argued that without a posting date on the website, it's possible Menendez's staff added that section only after he was charged, and therefore it was not relevant to his state of mind during the seven years prosecutors say the bribery scheme took place.

"I'm only suggesting that maybe ... he says I don't want to help anybody out of the state because look at the trouble it's gotten me into," said Lowell. "That's like even in a civil case somebody fixing the sidewalk after somebody has fallen."

Koski admitted he couldn't establish when exactly it was posted on the website, so Walls kept it out.

'Smears'

When prosecutors said they wanted to play a 2013 interview Menendez did with CNN's Dana Bash, an attempt by the defense team to keep it excluded would have been expected. Instead, Lowell tried to persuade Walls to have it played in full.

In the clip, Menendez defended his delayed reimbursement of rides on Melgen's private jet, but denied that he purchased the service of prostituted women at sex parties in the Dominican Republic and called them "smears" pushed by "right-wing blogs."

Walls ultimately ruled the prosecution had to use an edited clip of the interview, cutting out the portions on smears and prostitutes -- over the objections of the defense team who argued it should all stay in so that the jury could understand the the full "context" of the period of time in which the question was asked.

"I get the sense that the defense just wants me to totter and let this case go into smears about other allegations which are not part of the indictment, nor part of the matters that I have been hearing by way of production of evidence," Walls said. "And I am not going to let you get into a discussion about smears."

'Drowned by Lucentis'

Throughout the trial, defense attorneys have tried to poke holes in the prosecution's claim that Menendez wrongfully pressured federal officials to intervene in a multimillion-dollar dispute Melgen had with Medicare over his billing practices for an eye drug called Lucentis.

Federal regulations at the time approved the drug for "single-use" only, meaning that each vial should only be used for a single patient, but the doctor used the "overfill" from the vials to treat up to three patients -- known as "multi-dosing" -- and then billed Medicare three times, as if a separate vial was purchased for each dose when he only purchased one.

The defense team has wanted to show the jury that Medicare was only billed for the units administered to the patient, not per vial -- so the practice was "revenue neutral" to Medicare. Plus, other drugs, such as Botox, weren't treated the same way -- resulting in a windfall for the drug companies when it came to Lucentis -- and hence, explaining why Menendez decided to intervene on policy grounds.

But Walls has sharply limited each of these avenues for cross-examination, telling defense attorneys at one point he was "legally sick and tired of listening to it."

"It can be used, as I've stressed, eventually by the jury to determine whether there was or was not evidence of criminality reflected by way of criminal intent by these defendants," Walls said. "We are being drowned by Lucentis."

'The value of the bribe'

Prosecutors say Menendez reached out to high-level officials at the State Department to help Melgen resolve a contract dispute with the government of the Dominican Republic.

Melgen had acquired a company that contracted for screening cargo at the island's ports, but the Dominican Republic government had refused to honor the agreement.

Prosecutors tried to introduce "revenue projections" for the contract from Melgen's accountant, purportedly showing it could be worth up to $109 million.

"We are offering it to show the value of the bribe, the value of the official act that Dr. Melgen was paying for," prosecutor Amanda Vaughn said.

Defense attorneys argued, however, the "number crunching" should be excluded because it's "just guesswork," and Walls agreed.

A similar tactic was attempted when prosecutors urged Walls to allow them to show the value of Menendez's help on Melgen's billing dispute with Medicare.

The doctor had been hit in 2009 with a $8.9 million repayment demand related to his billing Medicare for Lucentis, and prosecutors sought to introduce evidence that Melgen continued the "multi-dosing" practice for a number of years after -- so the value of Menendez's help to resolve the dispute was ultimately closer to $40 million.

"The fact that Dr. Melgen kept doing it after 2009 is evidence that demonstrates the confidence he had that Senator Menendez would fix this problem for him," prosecutor Monique Abrishami said.

Walls eventually permitted prosecutors to elicit testimony that Melgen continued his billing practice "without specifying any amount" beyond the $8.9 million -- as that was the specific amount listed in the indictment.