A former Major League Baseball strength coach testified Tuesday that he only reluctantly told federal authorities about Roger Clemens’s alleged use of performance-enhancing drugs and did not initially intend to hand over evidence that prosecutors say tests have linked to the baseball legend.

For a second day, a subdued Brian McNamee spun out a story for jurors about how he helped Clemens use steroids and human growth hormone and why he decided to keep syringes, drugs and other items he said he used to inject the player in 2001.

McNamee, who began working with Clemens in 1998, and “The Rocket” both testified at Congressional hearings in 2008 examining a report by former Sen. George Mitchell about steroid abuse in baseball. Clemens is charged with perjury, obstruction of Congress and making false statements for his denials to a House panel that he had ever taken performance-enhancing drugs.

Reiterating what he told Congress, McNamee testified in the District’s federal court Tuesday that he injected the star pitcher on many occasions in Clemens’s Manhattan apartment and once in the New York Yankees’ clubhouse whirlpool room. The team hired McNamee as a strength coach at Clemens’s request.

In 2001, as they neared their final injection sessions, McNamee said he decided to keep some of the paraphernalia needed to give the shots. He said he stuffed a needle, gauze and other items into a crumpled beer can and kept it in a FedEx box marked “Clem” in his house for the next seven years.

McNamee said he saved the items to appease his wife, who was concerned that the coach would get in trouble if “something did go wrong” in his relationship with Clemens.

His wife warned that he would be the one “going down” if Clemens’s steroid use became public, McNamee said.

But McNamee did not turn the box over to federal authorities or Mitchell’s investigators when they questioned him in 2007. During those interviews, McNamee testified, he minimized the number of shots he gave Clemens in the hopes of reducing his friend’s culpability.

“I knew I’d hurt Roger even more and I didn’t want to do that,” McNamee told jurors.

By early 2008, however, McNamee had decided to turn over the materials he had used on Clemens. The strength coach said he became infuriated when Clemens allowed the television program “60 Minutes” to play a taped phone conversation between the two men in which McNamee spoke about his oldest son’s health problems. McNamee told jurors on Monday that his son had diabetes.

“It is beyond inhuman to do that to a kid,” McNamee testified. “There is no coming back from that.”

The former strength coach also testified about what he called the “creepy” experience of injecting Clemens’s wife, Debbie, with HGH in the couple’s Houston-area mansion. Debbie Clemens, who might testify, asked for the injections and Clemens stood by as McNamee reached around Clemens’s petite wife and gave her a shot near her belly button, the coach said.

“I can’t believe you’re going to let him do this,” McNamee recalled Debbie Clemens telling her husband.

“He injects me. Why can’t he inject you?” Clemens responded, according to McNamee.

McNamee said he never would have injected Debbie Clemens if her husband had not been present. That account is at odds with Clemens’s assertion to Congress that he learned about it after it happened.

Clemens’s lead attorney, Rusty Hardin, had about 15 minutes to cross-examine McNamee before court adjourned Tuesday.

Hardin tried to portray McNamee as benefiting financially from Clemens’s downfall, asking about a tie that advertised his friend’s nutritional supplement company that McNamee wore on the day he testified before a federal grand jury.

Hardin suggested that McNamee knew he would be the subject of media attention and said the strength coach subsequently tried to sell the tie he “wore to testify against Clemens.”

“That’s definitely possible,” McNamee said. “I forget if it was auctioned.”

Defense attorneys objected several times Tuesday when McNamee mentioned his relationship with Andy Pettitte, another star pitcher who has admitted to using performance-enhancing drugs with help from McNamee. But the defense team had successfully blocked prosecutors from telling jurors about McNamee’s involvement with Pettitte because of their concerns about “guilt by association.”

Judge Reggie D. Walton also ruled this week that jurors will be able to consider Pettitte’s wavering testimony about a conversation he had with Clemens about performance-enhancing drugs.