HOUSTON—Opening arguments were underway Wednesday in the trial of a woman accused of kidnapping and killing a 12-year-old Houston boy on Christmas Eve in 2010. Mona Yvette Nelson was charged with capital murder in the death of Jonathan Foster. Nelson has chosen to be tried by a judge, not a jury. Her attorney said he advised her against it. Police said the 44-year-old maintenance worker kidnapped and killed Jonathan, then burned his body. Nelson admitted to discarding the boy’s body, but said she did not kill him. Wednesday was an emotional day in court as Jonathan’s mother took the stand....