There's only one answer...

Becky entered the room and saw the kids.
"What are you doing here? The police let you in. I don't. Now get lost."
Jasper looked at her. "You just sent them away coz' you're hiding the truth. And... I know how you did it!"

She was shocked. But she remained as cool as a cucumber.
"You haven't got proof young man. Stop pointing at me. That's rude."
Jasper looked at her. "You were at a party and left and came back after 10 mins. During the ten minutes, you killed Mr. Grecia."
"What? You know well that even I can't go from the party and back again in 10 mins if I had to go to this house. Ask the maid, no one came here and no one came out."
"That's because you didn't kill him here. You killed him somewhere else, closer to the place of the party."
Nicah suddenly got the idea. She looked at the fingerprints on the window. You're really smart Jasper. Joshua, Yanna and Jem were clueless at the clues they have found themselves.
Nicah continued, "We are not looking for where you were. We are looking for where the victim was. See those fingerprints on top?"
The rest looked up. Joshua couldn't see, he was too short.
Jasper said, "Why would there be fingerprints on the top. Simple, the victim was trying to get out of the window."
Jem continued, "So the victim went out of the window and jumped out, it's an easy jump anyway."
Yanna replied, looking at the victim closely. "He went to a phone booth near you and called your cellphone. He gave you an address and you followed."
Joshua said, "You fought him but managed to win. You placed him carefully in the car and went back to the party. After that, you came to the house, put him in the bag you had your housemaid bring and brought him up. Knowing your sister was coming back, you rushed up here, leaving two marks on the wood and an overturned carpet."
Jasper summarized, "Now you left it all to acting."

Becky said, "Hahaha. Great theory kids, but you can't back it up."
The police came inside. "Who did it?" He asked the kids.
Yanna remembered something. "Ma'am, may I borrow your car keys?"
Becky gave it to her.
Yanna led them all down to the garage.
"Ma'am, here's the proof that you did it."

With a click of a button, the trunk opened, and inside were flowers.
"They're the same smell as the ones in the room."
The police examined all the facts. "I'm sorry ma'am, you're the one." And they handcuffed her.
Jem just asked one last thing, "Why did you do it?"
Becky answered, "It was because he threatened to kill me. He said I was a nuisance to him and he wanted me gone. But, of course, I stayed." She choked with tears. "Threatened by him, I started training for karate. Then yesterday, he called me, and I didn't know why. So I just went, and there he was, waiting for me. And I found out, I killed him!" Tears dropped to the floor.

Nicah decided that people won't believe kids these days, especially a small one (Joshua). So she told the police not to put their names on the newpaper or something. And so, they all rode Jem's car, and drove bcak to Jasper's "mansion."

EPILOGUE

Joshua checked his email. A new email.

From "CarlosP."
Subject: "Apoptoxin"