The widow of the Navy Seal depicted in the Oscar-nominated film American Sniper has given emotional evidence about her final moments with her husband.

Taya Kyle was a prosecution witness in the murder trial of the ex-marine accused of fatally shooting Chris Kyle and Chad Littlefield two years ago at a Texas gun range.

The trial in the small town of Stephenville has attracted national attention with the recent release of the blockbuster movie based on the memoir of the sniper who served four tours in Iraq.

Ms Kyle told jurors that as her husband left to go to the shooting range in February 2013, they gave each other a hug and kiss.

A lawyer for the accused, Eddie Ray Routh, said earlier in opening statements that Routh's insanity was so evident that Mr Kyle and Mr Littlefield exchanged texts expressing alarm as the three rode together to the shooting range.

The court heard how Mr Kyle had texted "This dude is straight-up nuts", shortly before he was shot dead.

But prosecutors say that even with a history of mental illness, Routh still knew right from wrong.

The case has drawn intense interest, largely because of Mr