GALVESTON, Texas -- A Walmart clerk told jurors a man and his wife bought a plastic storage box that a child's body was later found in, along with cleaning supplies used to conceal her death, KPRC Local 2 reported Friday.

Defense attorneys concede Royce Zeigler II helped in the coverup, but insist he didn't kill Riley Ann Sawyers.

Riley Ann's body was found floating in a container in Galveston Bay last October.

"They will show all this great tampering of evidence stuff and call that proof that Royce killed this baby," attorney Dee McWilliams said. "But it isn't. That's what we've been saying from day one."

The defense claims Zeigler's wife, Kimberly Trenor, beat Riley Ann to death. But Thursday, the child's grandmother testified that the girl was never spanked until her mother married Zeigler.

Friday, Zeigler's co-workers testified that he often complained about the child's boisterous behavior and Trenor's failure to discipline her.

Several described Zeigler as immature and said he regularly showed up late or called in sick. He often fell behind in his work, co-workers said.

Scott Estes said Zeigler's irrational behavior made him uneasy and that led Estes to nickname Zeigler "Psycho."

At a company picnic held just eight days after Riley Ann's death, Angela Zenon testified that Zeigler and Trenor appeared happy and playful. The couple socialized, drank and played softball with other employees. Neither, according to witnesses, showed any sign of stress or remorse for the girl whose body was at that time still hidden in a storage shed.

Trenor has already been convicted of capital murder.