How to Find Fingerprints


by Sandy Peterson


 

FINGERPRINT LAB INSTRUCTIONS




PART I - Balloon Prints

Materials:   White balloons       Fingerprint ink pad       Marker
Procedure:

1.Partially inflate a balloon.  Do not tie it off.

2.Open fingerprinting pad and gently roll one fingertip.

3.Apply finger to balloon surface near the center (where the balloon will expand the most), being careful not to smudge or twist while lifting the finger from the balloon surface.

4.Each group member should place one print on the balloon.

Inflate the balloon and mark each print with your name, hand     (right or left) and fingerprint pattern - ulnar loop, plain arch…

      5. Circle and name 4 different minutiae on each print.




PART II - Graphite Prints (Plastic Prints)

Materials:  Pencil      Paper        Transparent Tape       Index cards    

Procedure:

1.Hold the pencil at an angle on paper and fill a small area with graphite.

2.Roll the tip of one finger over the shiny graphite, making one or two passes. Good technique demands including the entire fingertip, edge to edge and down to the area of the first joint. Keeping the paper at the edge of the table will make this easier.

3.Have your partner pull 2 – 3 inches of tape, while only touching the ends and keeping the sticky side up.

4.Roll your graphite-covered fingertip onto the tape.

5.Carefully place your fingerprint on an index card.

6.Label each print with the type (plain whorl, radial loop..), hand (R or L) and name.

7.Repeat for each person in the group using the same card.





PART III - Inked Prints

Materials:       Ink Pad       White Paper        Fingerprint Card

Procedure:

1.On a sheet of scrap paper, practice rolling your lab partner’s prints.  Remember the techniques demonstrated in the video. Good technique demands including the entire fingertip, edge to edge and down to the area of the first joint. Keeping the paper at the edge of the table will make this easier

2.When rolling onto the paper, make one smooth, even motion. Look at the reference paper showing good and bad prints.

3.Have your teacher check your work.  When you feel comfortable with your technique, roll a full set of prints on the fingerprint card.  One card per person.

4.When the prints are dry, label each print pattern.

5.Determine your primary ID, showing your work.





PART IV – Lifting Prints

Materials:   Ceramic Tile, Index cards, Packing Tape, Magnetic Powder, 
                        Magnetic Powder Wand

Procedure: 

1.Lifting prints takes time and patience.  We will use magnetic powder (contains iron) since it works well on nonporous surfaces like glass and is less messy than other powders.

2.Obtain a ceramic tile, if needed wash and dry it well.
Hold it by the edges only.

3.Rub a finger over the surface of your forehead or some place where you will pick up skin oils.  Make some prints on the tile.

4.If you are not sure how to use the wand ask for help. Lightly brush a very small amount of powder over the print.  Too much or too little powder can make it difficult to see the minutiae.

5.Take a piece of packing tape and roll the edges to help you control it.  Do not touch the sticky side of the tape.  Place the tape over the entire print and lightly rub your finger across the tape, forcing out all the air bubbles.  Lift the piece of tape off the tile and place it on an index card.  Label the card with your name. 

6.Each person in the group should lift a fingerprint.





PART V – Cyanoacrylate fuming (Super glue)            POISON, CAREFUL!


Materials:  Super glue     Plastic bag      Plastic film canister or lid    
                                     Hair blow dryer

Procedure:

1.Place several oiled fingerprints on the film canister lid then lower it into a labeled plastic bag.  One canister lid per group.  Super glue will react with the fats and oils in the print.

2.Keeping the lid to one side, squeeze 5 – 8 drops of super glue in the corner of the bag and puff it with a bit of air (do not inhale the fumes!!).  The print on the lid should not touch the sides of the bag.

3.Quickly close the bag and let it sit for 20 – 30 minutes.

4.If the print (white in color) does not develop, heat the bag with a blow dryer.  Adding a moist (not wet) bit of paper toweling will also help.

5.Show your developed prints to your teacher so you can be given credit.





PART VI – Ninhydrin            POISON, CAREFUL!


Materials:    Fume hood    Gloves    Paint brush    Ninhydrin solution
                                             Index card

Procedure:

1.Make several latent prints on a labeled index card – one card per group.

2.Careful, ninhydrin can react with the amino acids in your skin and turn it purple/blue as it will when it reacts with the amino acids in the print.  Wear gloves and keep the solution away from open flames.  While under the fume hood, dab the print with a small amount of ninhydrin.  Do not use too much pressure.

3.Leave the card at the side of your lab table to dry for 24 hours.
     





PART VII – Iodine Crystals          POISON, CAREFUL!


Materials:  Small strip of index card     Iodine crystals in a closed jar
                                            Fume hood       Gloves

Procedure:

1.Place several latent prints on a labeled strip of index card - one card per group.

2.While under the fume hood and while wearing gloves, place the strip into a small jar containing iodine crystals.  Do not breathe the vapors!  Quickly close the lid and allow the print to develop for 5 – 10 minutes.  

3.Use forceps to remove the paper from the jar.  Show the print to your teacher to be given credit.   Iodine sublimes and will quickly leave the paper.  (Starch spray can be used to help save the print.)





PART VIII – Silver Nitrate (AgNO3)          POISON, CAREFUL!


Materials:     Fume hood       Silver nitrate solution      Paint brush      
                                         Index card

Procedure:

1.Place several latent prints on a labeled index card - one per group.

2.While under the fume hood and while wearing gloves, dab the print with a small amount of silver nitrate solution.  Silver nitrate (AgNO3) reacts with salt (NaCl) on the skin and will change your skin and the print a black or reddish-brown color.

3.Allow the card to dry at the side of your lab table.





PART IX – Fingerprint ID cards


Materials:    Hand lens      Fingerprints

Procedure:

1.Identify the pattern in each print and answer the questions in 2.

2.a. With the information given, why was it impossible to
      distinguish ulnar and radial loops?
b. How are loops, arches, and whorls distinguished?





PART X  -  Identify a suspect with fingerprints

Materials:    Hand lens     Crime scene and suspect fingerprints

There has been a break in at Mr. Johnson’s home.  Several pieces of electronic equipment were stolen as well as some expensive jewelry.  The crime scene investigators were able to find two sets of fingerprints on the bookcase where the TV set was located.  Neither print matched any of the occupants of the home fingerprints.  A page of fingerprints of criminals who’s M.O. matched that of the crime scene was complied for comparison.  Using the page of possible suspect’s prints and crime scene prints determine which person was responsible for the crime and answer the questions.


Questions:

1.Which suspect, if any, matched the crime scene prints (remember you are to match minutiae patterns)?

2.List 4 minutiae and their location that helped narrow the identification of the criminal.