Karmelo Anthony Trial

If anyone followed, this was the case where the African-American kid in Texas stabbed another kid after being confronted at a track meet. I am (probably in vain) trying to avoid any sort of social commentary. But I did have real questions about the process.

1. The defense didn't present any sort of expert testimony. I thought this was odd, because they seemed to be well funded and the facts were pretty straightforward. The entire question was self defense.
2. After the verdict, they moved directly to a sentencing hearing. The defense put on his mom and asked her a couple questions, and that was it.
3. I understand Texas has a special law where after a murder conviction, the defense can basically ask to lower it to manslaughter. They did this, but presented no other evidence.
4. I'm not trying to criticize the defense, more so trying to understand the system in Texas. Is there some limitation on the defense? Some benefit I'm not seeing? I live in Ohio and the idea that sentencing on a murder case would be held in basically enough time to grab a sandwich boggles my mind.