What is DNA evidence?

Question

If the police were to find DNA evidence at a crime scene, in what form would this be? Is it from blood, saliva, other bodily fluids? Or can you leave your DNA just by touching something?

The reason I ask is I'm not sure that the DNA database will be effective in solving crimes, but I don't really know enough about the DNA as forensic evidence issue.

Will be grateful for any enlightenment please. :)

Answer 1

In 1996, Gerald Parker—then in a California prison on a parole violation stemming from a 1980 sentence for raping a child—was charged with the rapes and murders of five women between December 1978 and October 1979 and the murder of a fetus during a rape in 1980. DNA samples from the crime scenes were run through California's sexual assault/violent offenders database, and four of the cases were found to have been committed by the same perpetrator. After DNA tests linked Parker to the victims, he confessed to the crimes. He also confessed to a similar, fifth crime for which Kevin Lee Green had been wrongly convicted and had served 16 years in prison.

DNA is similar to fingerprint analysis in how matches are determined. When using either DNA or a fingerprint to identify a suspect, the evidence collected from the crime scene is compared with the "known" print. If enough of the identifying features are the same, the DNA or fingerprint is determined to be a match. If, however, even one feature of the DNA or fingerprint is different, it is determined not to have come from that suspect.

In human cells, DNA is tightly wrapped into 23 pairs of chromosomes. One member of each chromosomal pair comes from your mother, and the other comes from your father. In other words, your DNA is a combination of your mother's and your father's. Unless you have an identical twin, your DNA is unique to you. This is what makes DNA evidence so valuable in investigations -- it's almost impossible for someone else to have DNA that is identical to yours.

Authorities can extract DNA from almost any tissue, including hair, fingernails, bones, teeth and bodily fluids. Sometimes, investigators have DNA evidence but no suspects. In that case, law enforcement officials can compare crime scene DNA to profiles stored in a database. The most commonly used database in the United States is called CODIS, which stands for Combined DNA Index System. CODIS is maintained by the FBI. By law, authorities in all 50 states must collect DNA samples from convicted sex offenders for inclusion in CODIS. Some states also require all convicted felons to submit DNA.

Hope this helps!

Answer 2

DNA is from things which where a part of the person. Just touching might not leave enought unless there where some skin cells left. You have to have a certain amount to make a decent test. Anything from a person, hair, blood, saliva, skin, sweat and just anything which comes out or off the body. If there was a data base with everyone in it, then you have a chance of knowing who did the crime. But I always carry some of my exs hair with me to leave at the crime if I do one ;)

Answer 3

dna can be found in many living or onceliving forms of tissue. usually, this is in the form of:
- skin tissue under fingernails (a fight where scratching occured)
- blood, in murders.
- bones, when corpses are found, and dental records cant be found.
- hairs
- or even in the case of rape, sperm.

now people usually think that dna evidence is an exact match. it actually isnt. eventhough everyones dna is unique. the testing in dna, only tests a number of dna markers. about two in 40.000 people will test the same when jsut testing on these markers. this is a high enough margin to support leeds that have already been layed.

a dna database, especially nationwide, is therefor hard to realise. as people might be arrested on just the assumption because they have been a previous offender.

Answer 4

i would think that anything that has your dna would be dna evidence

you are correct by naming saliva, blood and bodily fluids
Hair would also be something that would have your dna

I dont think that you can leave dna by touching something unless you leave any of the items mentioned above at the site as well.

you can leave a fingerprint at a scene which im sure they would be able to match if you are in the police database.

hope this helps

Answer 5

Anything a perpetrator leaves behind at a crime scene with his DNA on it, like strands of hair, skin fragments, blood, seman, , saliva, or any other types of bodily fluids.

Answer 6

DNA is found in blood, saliva, semen, and sweat. You can leave DNA behind by touching something, if you shed skin cells when you touch it.

Answer 7

forensic science could track you down pretty much with saliva, hair sample, blood, fingerprint etc....
DNA database i really effective in crime they track you down know who you are and having your information in a database they could find you again.
unless you had some major changes, maybe sex change , rip off your finger tip skin etc.... hope that help u

Answer 8

anything that was once part of or attached to the human body that remained there at the seen. hair,blood,sweat,sperm,fulids, even skin cells. anything really, with all of the modern tech. now a days, there is no such thing as "the perfect crime"