The Case of the Lost Explorer

Davis was talking with his friend Betty over lunch. The topic of the conversation turned to puzzles.
“Do you like deductive reasoning problems?” She asked him.
“Of course I do,” he replied as he drank his coffee. “They come with the job all of the time since I am a detective.”
“Good,” she said. “Then I have one for you. An explorer in Africa was captured by a hostile native tribe. The chief decided that he should be put to death. As a last conciliatory gesture, the chief decided to give the explorer a final choice in how his life would end. The man was to be given the opportunity to say one final sentence. If it was true, he would be impaled by spears. If it was false, he would be trampled by elephants.”
“The question is this-what would be the best sentence that the explorer could say in order to confuse the chief and get himself freed?”

WHAT DID DAVIS SAY?

THE ANSWER
“I must admit that I have heard riddles like this before,” Davis said. “I believe that he should say something like, “I will be trampled by elephants.” This way, if the tribe actually does have him trampled by elephants, then his sentence was actually true and he should have been impaled by spears instead. However, if the chief chose to have the explorer impaled by spears, then his sentence would have been false. Supposedly by making a statement like this, the man will succeed in totally fooling the chief into not making any decision at all regarding his execution and the tribe will eventually let him go. Am I right?”
“As usual,” Betty sighed.