The rarer the surname, the easier this technique becomes to secure a match with over a 75%  probability, reducing as the surname becomes more prevalent, so a preferred suspect would not be called Smith.
But this forensic advancement used in the Zodiac case could shake the murderers family tree to its roots and literally drop the killers name directly into the palms of our hands.

The Pigpen Cipher shown here on Wikipedia, is of course a simple substitution cipher and would explain the use of the Zodiac's liking for the rotated V symbol present throughout the 340 Cipher, as well as the variants he used such as the capital i with the dot on the left, the squares, circles and triangles etc, but as everybody knows the 340 cipher is far from simple, if indeed it is a genuine cipher in its entirety. But the Pigpen Cipher can be adapted and does not have to be rigid, it is possible to place the letters in any form of arrangement of your design and after each cipher symbol or letter is decoded the whole arrangement can be rotated, reversed or basically altered in any way the designer chooses. In this way the same letter or symbol in the code can produce a result of all 26 letters and unless you can find the key it is a near impossible task.
The Zodiac may have disguised the key somewhere in his many cards and letters, possibly indicating something with his photocopied keys in the Eureka Card for example, but the search goes on into its 44th year.     

decrypt. Plus the numbers allocated to each letter could shift by any amount each time or at predetermined times.
The possibilities are infinite, but realistically the Zodiac must have known that an impossible cipher is pointless, so if it were genuine, a key would be attainable and it could be resting harmlessly somewhere within the letters or cards, it is just knowing where to look.
PIGPEN CIPHER TOOL 
MASONIC SYMBOLS VIDEO at 18 minutes into video
FBI CODE ANALYSIS

The 340 cipher has confounded all attempts at decryption during the preceding 44 years. Five months after the November 8th Dripping Pen card and 340 character cipher, on April 20th 1970, the Zodiac Killer mailed the My Name is Cipher, stating "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you. My name is....." 
 
Based on his wording in the cracked 408 cipher: "I will not give you my name because you will try to slow down or stop my collecting of slaves for my afterlife", it may be possible he signed off the 340 cipher with a phrase something like "I will not tell you who the Zodiac is", bearing in mind the positioning and appearance of the symbols on the last line.

We know that he placed what appeared to be three circled 8's on the 13 Symbol cipher, but why did he circle them? Was it to highlight the fact they had increased significance? In a previous article we highlighted the symmetry contained within the 13 Symbol cipher.  https://www.zodiacciphers.com/zodiac-news/the-symmetry-of-the-13-symbol-cipher

On the right we have lined up the alphabet over the top of the cipher. Now calculate numerically the difference in each column. ie: C to N produces a difference of 11, whereas B to E produces a difference of 3. Non alphabetical symbols cannot produce a difference, so a zero is inserted. The resulting numbers produced have been color coded. The red section is before the first circled 8, the green section is after the last circled 8 and the blue section spans the first and last circled 8. Notice the perfect symmetry. The red and green numbers are identical, read forwards or backwards and the blue numbers again read identically in either direction, producing a mirror image. Is this a coincidence or is it by design?

So can we generate the same symmetry from the only apparent reference to the name ZODIAC on the final line of the 340 cipher, to provide us with that seamless link.
We will use the identical technique featured above, by alphabetically counting the numerical difference between the letters in the cipher and the key chosen. In this case, the key is the killer's pseudonym ZODIAC, because it is without doubt the most significant marker he placed on the 340 cipher - and it is difficult to believe he placed the 'near Zodiac'on the final line by sheer accident during the construction of the cipher. 

If we then count alphabetically, the numerical difference between the columns, ZOD produces no difference between the columns. ie: 000. The IAC element produces the numerical difference 888. The Zodiac Killer possibly took the 000 and 888, and incorporated these elements, in the form of three circled 8's into his following 13 Symbol cipher on April 20th 1970. Even the crossed circle and inverted Aries were carried forward. But is this proof of a link?

888 is a unique number, explained here in Wikipedia. In Christian numerology, the number 888 represents Jesus, or sometimes more specifically Christ the Redeemer. This representation may be justified either through gematria, by counting the letter values of the Greek transliteration of Jesus' name, or as an opposing value to 666, the number of the beast. In Chinese numerology, 888 has a different meaning, triple fortune, a strengthening of the meaning of the digit 8. For this reason, addresses and phone numbers containing the digit sequence 888 are considered particularly lucky, and may command a premium because of it. 

To Kill a Mockingbird, written by Harper Lee, was a hugely successful book published on July 11th 1960 and later adapted into a motion picture starring Gregory Peck two years later, portraying racial injustice and the innocence of youth from the backdrop of the fictional town of Maycomb, Alabama. This next section is not inferring the Zodiac drew any inspiration from this novel, however, it will outline some unusual coincidences between this work of fiction and two greeting cards mailed by the Zodiac, notably the October 27th 1970 'Halloween' card and the December 1990 'Eureka' or 'American Greetings' card.

​Kevin Robert Brooks noticed that the Asian characters at the foot of the 'Exorcist' letter could be rearranged to spell the words, 'To Kill'. These are obviously the first two words of this novel, but the 'Exorcist' letter also contained an extract from The Mikado about a bird, taken from Act II On a tree by a river- a little tom-tit in this case. 

To Kill a Mockingbird was widely used as an educational tool in many schools, in which one of the central characters was "Boo" Radley, a reclusive resident of Maycomb, who generated a constant source of suspicion and mystery from the local townsfolk, despite his later acts of disguised benevolence. Note BOO on the 'Halloween' card. He went by the name Boo Radley, but curiously his first name was Arthur. 

The alphabetical letters LAV letters are present together in the horizontal word SLAVES on the back of the card and underlined in the name Paul Averly on the envelope, but note the three letters at the intersection of the crossed PARADICE and SLAVES running vertically - they spell RAD,
The incorrect spelling of Paul Avery to Averly points towards LEY, to complete the character BOO RADLEY.

In the novel, a local resident by the name of Stephanie Crawford reported she was woken up one night and saw Boo Radley "looking straight through the window at her..... said his head was like a skull lookin' at her". On the tree around the knothole there are the words PEEK A BOO YOU ARE DOOMED.

The musical score to the original motion picture was composed by Elmer Bernstein. Three of the soundtracks are Creepy Caper/Peek-a-Boo, Boo Who and Tree Treasure. In the book, Tree Treasure was a hiding place in the knothole of a tree, where several items were found including a broken pocket watch, an aluminium knife and a ball of twine. These were placed there by Boo Radley for two local kids, Scout and Jem, to discover. The knothole in the tree represented Boo Radley's outlet to the world, and soon the children were to realize that Boo Radley was far from the monster he had been depicted. All the items he placed at intervals in the knothole came in pairs, except the twine - there were two packets of chewing gum, two polished coins, two miniatures of children, and the most interesting of all, was a knife and pocket watch, both on the same chain. Presumably two items, so Jem and Scout could have one each. The 'Eureka' card or 'American Greetings' card, mailed by the Zodiac Killer in 1990, was very similar to the 'Halloween' card in its design, both beginning with the phrase "From your secret pal". The 'Eureka' card included a photocopy, of not one, but a pair of keys on a chain. But who was the "secret pal" - the Zodiac Killer or Boo Radley?

​Incidentally, Scout and Jem build a snowman in the the Harper Lee novel, made initially from mud, but then layered with snow- a theme many believe is reflective of the racial overtones contained within the story. A snowman was depicted on the 'Eureka' card, with what appeared to be Groucho Marx imagery on the face. Jem and Scout created this snowman because of their dislike of a local resident down the street, much to the annoyance of their father Atticus Finch, who told the children to disguise it because it so resembled the local resident they were poking fun at. Their solution was to place Miss Maudie Atkinson's hat on it (she lived across the street from Atticus Finch and his family). The resident they so disliked was called MR AVERY- now that is a coincidence- along with release date of the film: December 25th 1962, in Los Angeles, California. Happy Holidays.