LAW ENFORCEMENT CAN tell when suspects are lying, usually beginning with an initial emergency call or first interview.

“The 911 call (in America) and initial statements are among the most important pieces of evidence should a case go to trial,” said Stacy Dittrich, a former Ohio police detective, crime expert and author. “The entire case can build from those few sentences.”

Dittrich has appeared on Nancy Grace, CNN and E! to discuss headline-making cases and explain what happens behind the yellow tape. She told us police can usually tell if a suspect is lying–even if their story seems to line up.

Here are the most tell-tale signs, revealed.

A pre-emptive emergency call: Criminals sometimes call police very early to cover their bases. For instance, a man with a missing spouse might call police within a couple hours to say something is wrong. “The first question the detective is asking is why they’re assuming something is wrong because not getting ahold of someone right away is pretty normal,” Dittrich said.

The emotions don’t fit: even if what a suspect is saying on the call appears to be true, their tone is a big tip-off to police, Dittrich said. For instance, a calm demeanour while reporting a home invasion could indicate something is amiss because “most people are hysterical in that kind of situation”.

Not answering “yes” or “no”: an innocent person will usually answer questions with a direct yes or no. Not so for criminals, says Dittrich. When asked “are you involved in this murder?” they are likely to give a long answer like “I swear on my mother’s grave and all my children I didn’t.” This is a way of stalling: even though they tell themselves to lie, they can’t quite follow through.

Too many details: A criminal usually carefully plans their story in advance, anticipating that they’ll eventually speaks with detectives. A 911 call with too many details about the suspect, such as what they did that day or whether they’re happy with their significant other, is a red flag because it shows the person put thought into his or her story.

Lying about small stuff: Even the most innocuous statements can reveal inconsistencies, Dittrich said. A suspect talk of watching a television show in his or her alibi statement, but the show didn’t air that night. Lies about small stuff usually culminate in bigger evidence against the accused.

Referring to a missing person in past-tense: Most people hold out hope that their missing loved one will be found alive. Referring to a person in past tense, saying “I really loved her” or “he and I were happily married,” is incriminating, Dittrich said.

Saying “huh?” : When police ask a direct question, such as “Did you steal those items?” a guilty suspect will often pretend not to hear in order to stall and come up with a story, Dittrich said. Instead of answering a very direct question they say “huh?” or “what do you mean?” Dittrich said.

Helpfully offering another explanation: a suspect will often try and mislead detectives by putting another suspicious person on the investigation’s radar, Dittrich said. If a person denies a kidnapping but mentions a creepy man in a van, it’s important to see if there’s any other evidence of such a person existing. If there’s not, chances are the suspect made up a story to deflect the blame.

Most criminals destroy themselves with their own statements. The ones who are acquitted despite ample evidence are “sociopathic” enough to convince themselves that the lies are reality, Dittricht told us, citing Casey Anthony, the infamous Florida mother acquitted of murdering her daughter.

“It’s haunting because the people who get away are the ones deranged enough to believe their own lies,” Dittrich said.