The case of Zakaria M. Oweiss was unusual to begin with -- a Potomac physician accused of fatally beating his wife with a hammer because he suspected her of infidelity. But it got even more strange during his trial this week as prosecutors alleged that Oweiss stole and disposed of evidence while sitting in the courtroom.

The evidence -- which prosecutors consider important to their case -- is a car key, one of several on a key ring. Oweiss, at his murder trial in Montgomery County Circuit Court, was allowed to examine the key ring as he sat at the defense table Wednesday.

The car key was attached to the ring when it was handed to Oweiss, prosecutors said. Later in the day, they noticed the key was missing. They angrily accused Oweiss of stealing it, which he denied. And then the case took another odd turn.

The allegation triggered a two-day trial-within-a-trial -- a hearing outside the jury's presence to determine what happened to the key. In one of several acrimonious exchanges between the defense and prosecution over the missing evidence, Oweiss's attorney accused the state's attorney's office of mishandling items before and during the trial and urged the judge to declare a mistrial, citing "prosecutorial misconduct."

The defense even suggested that the key had never been in the courtroom.

In the end, Judge S. Michael Pincus decided to allow jurors to hear each side's version of the dispute and make up their own minds about what happened. They heard tape-recorded testimony from Oweiss, given outside of their presence.

"If, in fact, you had taken that key off [the ring], you would tell us?" asked Deputy State's Attorney Katherine Winfree.

"Yes, I would," Oweiss replied.

The judge did not allow the jury to hear Winfree's sarcastic follow-up: "Just like you would tell us whether or not you killed your wife."

It was the only time jurors would hear from Oweiss in the trial. Each side rested its case yesterday, and the defendant did not testify in person before the jury.

Oweiss, 58, a gynecologist, is charged with killing Marianne Oweiss, 49, on Aug. 15, 2001, in their home on Kentsdale Drive. Numerous witnesses testified that the victim had engaged in extramarital affairs.

Defense lawyer Peter Davis suggested that the couple's two grown sons, Omar and Amin, were incensed by their mother's role in their family's disintegration and that both had motives to kill her. Davis noted that Omar Oweiss was in the family home the day of the killing.

The missing key was to a red Volkswagen Jetta. The key could have a bearing on whether jurors believe Oweiss secretly parked the Jetta near the home that morning so that he could sneak into the house undetected, as prosecutors have argued.

After learning that the key was missing Wednesday, Winfree asked the judge to have Oweiss searched -- though she also suggested that the defendant had plenty of opportunity to dispose of the key during breaks or at lunch. Without objection, Davis allowed his client to undergo a search and be questioned under oath.

But Davis also challenged the state to prove that the key had ever been on the ring that was presented in court. And he accused prosecutors of lapses in procedures for handling the other evidence. For example, he said the prosecution had improperly removed a remote-control door unlocking device for Marianne Oweiss's Jeep from the same key ring and returned it to Omar Oweiss before the trial began.

Yesterday, the courtroom clerk and a sheriff's deputy testified that Davis had asked for permission to inspect the key ring with the Jetta key early Wednesday. The clerk handed Davis an envelope with the items, and Davis placed the items on the defense table. Both testified that they witnessed Oweiss moving his hands under the defense table while holding the key ring.

Under oath, Oweiss denied removing the key. Nancy Luque, a lawyer who entered the case to assist the defense in dealing with the key controversy, said Oweiss, a Muslim, habitually held his hands under the table while praying with prayer cards and beads.