Pretoria, South Africa (CNN) -- An emotional Oscar Pistorius apologized Monday to the family of Reeva Steenkamp, the girlfriend he killed on Valentine's Day last year, saying he woke up thinking of them and praying for them every day.

"I would like to take this opportunity to apologize -- to Mr. and Mrs. Steenkamp, to Reeva's family -- to those who are here today who knew her," Pistorius said as he took the stand for the first time at his murder trial.

"I can't imagine the pain and the sorrow and the emptiness that I have caused you and your family. ... I can promise you that when she went to bed that night, she felt loved," he said, his voice breaking as if he was fighting back tears.

It was the first time he has spoken in public about Steenkamp's death, which he says was an accident. He pleaded not guilty to murder when the high-profile trial opened last month.

Steenkamp's mother, June, sat stony-faced in court as South Africa's onetime Olympic golden boy choked out his statement.

Judge Thokozile Masipa also betrayed no emotion as Pistorius spoke but did once ask him to talk louder, saying she could hardly hear him.

Monday was the first day of the defense phase of the trial, following three weeks of prosecution in March.

Pistorius, who says he mistook Steenkamp for an intruder in his house in the dark, testified that he has been suffering nightmares since the killing and wakes up smelling blood.

Now, provide a numbered list of answers to these questions:

1. Where is this happening?
2. What is happening?
3. what was her name?
4. when did it happen?
5. what phase is it in?
6. Did he speak?
7. What did he say?
8. What did he say happen?
9. how long was the first phase of the trial?
10. Why was it high profile?
11. from what country?
12. Who was presiding over the case?
1. Pretoria, South Africa
2. Oscar Pistorius murdered his girlfriend
3. Reeva Steenkamp
4. Valentine's Day last year
5. defense phase of the trial
6. yes
7. I can't imagine the pain and the sorrow and the emptiness that I have caused you and your family. ... I can promise you that when she went to bed that night, she felt loved,"
8. he mistook Steenkamp for an intruder in his house in the dark
9. a month
10. he is an olympian
11. South Africa
12. Judge Thokozile Masipa