Here's an interesting article on WIKI
Conviction for murder in the absence of a body is possible; although historically, cases of this type have been hard to prove, the prosecution must rely on other evidence, usually circumstantial. Recent developments in forensic science make it less likely that such a murder will go unpunished.
http://en.wikipedia.org/wiki/Murder_conviction_without_a_body
And this
Prosecutions for murders without bodies were once extremely rare, according to DiBiase, who traces the earliest documented case in the United States to 1819, when brothers Jesse and Stephen Boorn were convicted of murdering their brother-in-law, Richard Colvin, in Manchester, Vt.
More than 300 such cases that have gone to trial in the United States since, more than 90 percent of them resulting in a conviction, DiBiase said.
Although defense attorneys often try to convince jurors that no body means no proof a person is dead, DiBiase has found only one case, around 1886, in which a victim turned up alive after his supposed killer -- tried twice on charges he killed his lover's husband -- had been convicted and executed.
In the past decade, DiBiase said a surge in such murder prosecutions is largely thanks to advances in DNA technology, computer records and cell phone logs, and improvements in
forensics.
Juries have also become more sophisticated with the popularity of crime, law and forensic television shows, according to Donna Pendergast, assistant attorney general for the Michigan Department of Attorney General's office, who has successfully prosecuted several of these cases.
Pendergast says the enormous public appetite for forensics has led to jury pools full of people who "want to see every little
fingerprint."
She has convinced juries that a person was really dead even though no body was ever found, because the victim didn't access bank accounts or credit cards after they disappeared.
"Traditionally, a prosecutor would say: 'No body, we don't have a case,' " Pendergast said. "But now that people are seeing these cases can be won. ... It's not 'the perfect crime' anymore."
http://www.njherald.com/story/news/a0581-BC-US-BodylessMurders-2ndLd-Writethru-04-11-1117